diff --git a/backlog/tasks/task-261 - Fix-immersion-tracker-SQLite-timestamp-truncation.md b/backlog/tasks/task-261 - Fix-immersion-tracker-SQLite-timestamp-truncation.md
new file mode 100644
index 00000000..f900d685
--- /dev/null
+++ b/backlog/tasks/task-261 - Fix-immersion-tracker-SQLite-timestamp-truncation.md	
@@ -0,0 +1,29 @@
+---
+id: TASK-261
+title: Fix immersion tracker SQLite timestamp truncation
+status: In Progress
+assignee: []
+created_date: '2026-03-31 01:45'
+labels:
+  - immersion-tracker
+  - sqlite
+  - bug
+dependencies: []
+references:
+  - src/core/services/immersion-tracker
+priority: medium
+ordinal: 1200
+---
+
+## Description
+
+<!-- SECTION:DESCRIPTION:BEGIN -->
+Current-epoch millisecond values are being truncated by the libsql driver when bound as numeric parameters, which corrupts session, telemetry, lifetime, and rollup timestamps.
+<!-- SECTION:DESCRIPTION:END -->
+
+## Acceptance Criteria
+<!-- AC:BEGIN -->
+- [ ] #1 Current-epoch millisecond timestamps persist correctly in session, telemetry, lifetime, and rollup tables
+- [ ] #2 Startup backfill and destroy/finalize flows keep retained sessions and lifetime summaries consistent
+- [ ] #3 Regression tests cover the destroyed-session, startup backfill, and distinct-day/distinct-video lifetime semantics
+<!-- AC:END -->
diff --git a/src/core/services/immersion-tracker-service.test.ts b/src/core/services/immersion-tracker-service.test.ts
index e286f126..3134f129 100644
--- a/src/core/services/immersion-tracker-service.test.ts
+++ b/src/core/services/immersion-tracker-service.test.ts
@@ -5,6 +5,7 @@ import os from 'node:os';
 import path from 'node:path';
 import { toMonthKey } from './immersion-tracker/maintenance';
 import { enqueueWrite } from './immersion-tracker/queue';
+import { toDbTimestamp } from './immersion-tracker/query-shared';
 import { Database, type DatabaseSync } from './immersion-tracker/sqlite';
 import { nowMs as trackerNowMs } from './immersion-tracker/time';
 import {
@@ -185,7 +186,7 @@ test('destroy finalizes active session and persists final telemetry', async () =
 
     const db = new Database(dbPath);
     const sessionRow = db.prepare('SELECT ended_at_ms FROM imm_sessions LIMIT 1').get() as {
-      ended_at_ms: number | null;
+      ended_at_ms: string | number | null;
     } | null;
     const telemetryCountRow = db
       .prepare('SELECT COUNT(*) AS total FROM imm_session_telemetry')
@@ -193,7 +194,7 @@ test('destroy finalizes active session and persists final telemetry', async () =
     db.close();
 
     assert.ok(sessionRow);
-    assert.ok(Number(sessionRow?.ended_at_ms ?? 0) > 0);
+    assert.notEqual(sessionRow?.ended_at_ms, null);
     assert.ok(Number(telemetryCountRow.total) >= 2);
   } finally {
     tracker?.destroy();
@@ -504,7 +505,7 @@ test('rebuildLifetimeSummaries backfills retained ended sessions and resets stal
       episodes_started: number;
       episodes_completed: number;
       anime_completed: number;
-      last_rebuilt_ms: number | null;
+      last_rebuilt_ms: string | number | null;
     } | null;
     const appliedSessions = rebuildApi.db
       .prepare('SELECT COUNT(*) AS total FROM imm_lifetime_applied_sessions')
@@ -518,7 +519,7 @@ test('rebuildLifetimeSummaries backfills retained ended sessions and resets stal
     assert.equal(globalRow?.episodes_started, 2);
     assert.equal(globalRow?.episodes_completed, 2);
     assert.equal(globalRow?.anime_completed, 1);
-    assert.equal(globalRow?.last_rebuilt_ms, rebuild.rebuiltAtMs);
+    assert.equal(globalRow?.last_rebuilt_ms, toDbTimestamp(rebuild.rebuiltAtMs));
     assert.equal(appliedSessions?.total, 2);
   } finally {
     tracker?.destroy();
@@ -629,97 +630,89 @@ test('startup finalizes stale active sessions and applies lifetime summaries', a
     const startedAtMs = trackerNowMs() - 10_000;
     const sampleMs = startedAtMs + 5_000;
 
-    db.exec(`
-      INSERT INTO imm_anime (
-        anime_id,
-        canonical_title,
-        normalized_title_key,
-        episodes_total,
-        CREATED_DATE,
-        LAST_UPDATE_DATE
-      ) VALUES (
-        1,
-        'KonoSuba',
-        'konosuba',
-        10,
-        ${startedAtMs},
-        ${startedAtMs}
-      );
+    db.prepare(
+      `
+        INSERT INTO imm_anime (
+          anime_id,
+          canonical_title,
+          normalized_title_key,
+          episodes_total,
+          CREATED_DATE,
+          LAST_UPDATE_DATE
+        ) VALUES (?, ?, ?, ?, ?, ?)
+      `,
+    ).run(1, 'KonoSuba', 'konosuba', 10, toDbTimestamp(startedAtMs), toDbTimestamp(startedAtMs));
 
-      INSERT INTO imm_videos (
-        video_id,
-        video_key,
-        canonical_title,
-        anime_id,
-        watched,
-        source_type,
-        duration_ms,
-        CREATED_DATE,
-        LAST_UPDATE_DATE
-      ) VALUES (
-        1,
-        'local:/tmp/konosuba-s02e05.mkv',
-        'KonoSuba S02E05',
-        1,
-        1,
-        1,
-        0,
-        ${startedAtMs},
-        ${startedAtMs}
-      );
+    db.prepare(
+      `
+        INSERT INTO imm_videos (
+          video_id,
+          video_key,
+          canonical_title,
+          anime_id,
+          watched,
+          source_type,
+          duration_ms,
+          CREATED_DATE,
+          LAST_UPDATE_DATE
+        ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
+      `,
+    ).run(
+      1,
+      'local:/tmp/konosuba-s02e05.mkv',
+      'KonoSuba S02E05',
+      1,
+      1,
+      1,
+      0,
+      toDbTimestamp(startedAtMs),
+      toDbTimestamp(startedAtMs),
+    );
 
-      INSERT INTO imm_sessions (
-        session_id,
-        session_uuid,
-        video_id,
-        started_at_ms,
-        status,
-        ended_media_ms,
-        CREATED_DATE,
-        LAST_UPDATE_DATE
-      ) VALUES (
-        1,
-        '11111111-1111-1111-1111-111111111111',
-        1,
-        ${startedAtMs},
-        1,
-        321000,
-        ${startedAtMs},
-        ${sampleMs}
-      );
+    db.prepare(
+      `
+        INSERT INTO imm_sessions (
+          session_id,
+          session_uuid,
+          video_id,
+          started_at_ms,
+          status,
+          ended_media_ms,
+          CREATED_DATE,
+          LAST_UPDATE_DATE
+        ) VALUES (?, ?, ?, ?, ?, ?, ?, ?)
+      `,
+    ).run(
+      1,
+      '11111111-1111-1111-1111-111111111111',
+      1,
+      toDbTimestamp(startedAtMs),
+      1,
+      321000,
+      toDbTimestamp(startedAtMs),
+      toDbTimestamp(sampleMs),
+    );
 
-      INSERT INTO imm_session_telemetry (
-        session_id,
-        sample_ms,
-        total_watched_ms,
-        active_watched_ms,
-        lines_seen,
-        tokens_seen,
-        cards_mined,
-        lookup_count,
-        lookup_hits,
-        pause_count,
-        pause_ms,
-        seek_forward_count,
-        seek_backward_count,
-        media_buffer_events
-      ) VALUES (
-        1,
-        ${sampleMs},
-        5000,
-        4000,
-        12,
-        120,
-        2,
-        5,
-        3,
-        1,
-        250,
-        1,
-        0,
-        0
-      );
-    `);
+    db.prepare(
+      `
+        INSERT INTO imm_session_telemetry (
+          session_id,
+          sample_ms,
+          total_watched_ms,
+          active_watched_ms,
+          lines_seen,
+          tokens_seen,
+          cards_mined,
+          lookup_count,
+          lookup_hits,
+          pause_count,
+          pause_ms,
+          seek_forward_count,
+          seek_backward_count,
+          media_buffer_events
+        ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+      `,
+    ).run(1, toDbTimestamp(sampleMs), 5000, 4000, 12, 120, 2, 5, 3, 1, 250, 1, 0, 0);
 
     tracker.destroy();
     tracker = new Ctor({ dbPath });
@@ -734,7 +727,7 @@ test('startup finalizes stale active sessions and applies lifetime summaries', a
         `,
       )
       .get() as {
-      ended_at_ms: number | null;
+      ended_at_ms: string | number | null;
       status: number;
       ended_media_ms: number | null;
       active_watched_ms: number;
@@ -769,7 +762,7 @@ test('startup finalizes stale active sessions and applies lifetime summaries', a
       .get() as { total: number } | null;
 
     assert.ok(sessionRow);
-    assert.ok(Number(sessionRow?.ended_at_ms ?? 0) >= sampleMs);
+    assert.equal(sessionRow?.ended_at_ms, toDbTimestamp(sampleMs));
     assert.equal(sessionRow?.status, 2);
     assert.equal(sessionRow?.ended_media_ms, 321_000);
     assert.equal(sessionRow?.active_watched_ms, 4000);
diff --git a/src/core/services/immersion-tracker-service.ts b/src/core/services/immersion-tracker-service.ts
index 159f1b6c..276cd3d6 100644
--- a/src/core/services/immersion-tracker-service.ts
+++ b/src/core/services/immersion-tracker-service.ts
@@ -309,6 +309,9 @@ export class ImmersionTrackerService {
   private readonly eventsRetentionMs: number;
   private readonly telemetryRetentionMs: number;
   private readonly sessionsRetentionMs: number;
+  private readonly eventsRetentionDays: number | null;
+  private readonly telemetryRetentionDays: number | null;
+  private readonly sessionsRetentionDays: number | null;
   private readonly dailyRollupRetentionMs: number;
   private readonly monthlyRollupRetentionMs: number;
   private readonly vacuumIntervalMs: number;
@@ -365,46 +368,54 @@ export class ImmersionTrackerService {
     );
 
     const retention = policy.retention ?? {};
-    const daysToRetentionMs = (
+    const daysToRetentionWindow = (
       value: number | undefined,
-      fallbackMs: number,
+      fallbackDays: number,
       maxDays: number,
-    ): number => {
-      const fallbackDays = Math.floor(fallbackMs / 86_400_000);
+    ): { ms: number; days: number | null } => {
       const resolvedDays = resolveBoundedInt(value, fallbackDays, 0, maxDays);
-      return resolvedDays === 0 ? Number.POSITIVE_INFINITY : resolvedDays * 86_400_000;
+      return {
+        ms: resolvedDays === 0 ? Number.POSITIVE_INFINITY : resolvedDays * 86_400_000,
+        days: resolvedDays === 0 ? null : resolvedDays,
+      };
     };
 
-    this.eventsRetentionMs = daysToRetentionMs(
+    const eventsRetention = daysToRetentionWindow(
       retention.eventsDays,
-      DEFAULT_EVENTS_RETENTION_MS,
+      7,
       3650,
     );
-    this.telemetryRetentionMs = daysToRetentionMs(
+    const telemetryRetention = daysToRetentionWindow(
       retention.telemetryDays,
-      DEFAULT_TELEMETRY_RETENTION_MS,
+      30,
       3650,
     );
-    this.sessionsRetentionMs = daysToRetentionMs(
+    const sessionsRetention = daysToRetentionWindow(
       retention.sessionsDays,
-      DEFAULT_SESSIONS_RETENTION_MS,
+      30,
       3650,
     );
-    this.dailyRollupRetentionMs = daysToRetentionMs(
+    this.eventsRetentionMs = eventsRetention.ms;
+    this.eventsRetentionDays = eventsRetention.days;
+    this.telemetryRetentionMs = telemetryRetention.ms;
+    this.telemetryRetentionDays = telemetryRetention.days;
+    this.sessionsRetentionMs = sessionsRetention.ms;
+    this.sessionsRetentionDays = sessionsRetention.days;
+    this.dailyRollupRetentionMs = daysToRetentionWindow(
       retention.dailyRollupsDays,
-      DEFAULT_DAILY_ROLLUP_RETENTION_MS,
+      365,
       36500,
-    );
-    this.monthlyRollupRetentionMs = daysToRetentionMs(
+    ).ms;
+    this.monthlyRollupRetentionMs = daysToRetentionWindow(
       retention.monthlyRollupsDays,
-      DEFAULT_MONTHLY_ROLLUP_RETENTION_MS,
+      5 * 365,
       36500,
-    );
-    this.vacuumIntervalMs = daysToRetentionMs(
+    ).ms;
+    this.vacuumIntervalMs = daysToRetentionWindow(
       retention.vacuumIntervalDays,
-      DEFAULT_VACUUM_INTERVAL_MS,
+      7,
       3650,
-    );
+    ).ms;
     this.db = new Database(this.dbPath);
     applyPragmas(this.db);
     ensureSchema(this.db);
@@ -1604,6 +1615,9 @@ export class ImmersionTrackerService {
           eventsRetentionMs: this.eventsRetentionMs,
           telemetryRetentionMs: this.telemetryRetentionMs,
           sessionsRetentionMs: this.sessionsRetentionMs,
+          eventsRetentionDays: this.eventsRetentionDays ?? undefined,
+          telemetryRetentionDays: this.telemetryRetentionDays ?? undefined,
+          sessionsRetentionDays: this.sessionsRetentionDays ?? undefined,
         });
       }
       if (
diff --git a/src/core/services/immersion-tracker/__tests__/query.test.ts b/src/core/services/immersion-tracker/__tests__/query.test.ts
index de56cec9..44072646 100644
--- a/src/core/services/immersion-tracker/__tests__/query.test.ts
+++ b/src/core/services/immersion-tracker/__tests__/query.test.ts
@@ -44,6 +44,7 @@ import {
   EVENT_SUBTITLE_LINE,
   EVENT_YOMITAN_LOOKUP,
 } from '../types.js';
+import { toDbTimestamp } from '../query-shared.js';
 
 function makeDbPath(): string {
   const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'subminer-imm-query-test-'));
@@ -81,29 +82,13 @@ function cleanupDbPath(dbPath: string): void {
   }
 }
 
-function withMockDate<T>(fixedDate: Date, run: (realDate: typeof Date) => T): T {
-  const realDate = Date;
-  const fixedDateMs = fixedDate.getTime();
-
-  class MockDate extends Date {
-    constructor(...args: any[]) {
-      if (args.length === 0) {
-        super(fixedDateMs);
-      } else {
-        super(...(args as [any?, any?, any?, any?, any?, any?, any?]));
-      }
-    }
-
-    static override now(): number {
-      return fixedDateMs;
-    }
-  }
-
-  globalThis.Date = MockDate as DateConstructor;
+function withMockNowMs<T>(fixedDateMs: string | number, run: () => T): T {
+  const previousNowMs = globalThis.__subminerTestNowMs;
+  globalThis.__subminerTestNowMs = fixedDateMs;
   try {
-    return run(realDate);
+    return run();
   } finally {
-    globalThis.Date = realDate;
+    globalThis.__subminerTestNowMs = previousNowMs;
   }
 }
 
@@ -613,7 +598,7 @@ test('getTrendsDashboard returns chart-ready aggregated series', () => {
     ] as const) {
       stmts.telemetryInsertStmt.run(
         sessionId,
-        startedAtMs + 60_000,
+        `${startedAtMs + 60_000}`,
         activeWatchedMs,
         activeWatchedMs,
         10,
@@ -626,8 +611,8 @@ test('getTrendsDashboard returns chart-ready aggregated series', () => {
         0,
         0,
         0,
-        startedAtMs + 60_000,
-        startedAtMs + 60_000,
+        `${startedAtMs + 60_000}`,
+        `${startedAtMs + 60_000}`,
       );
 
       db.prepare(
@@ -644,7 +629,7 @@ test('getTrendsDashboard returns chart-ready aggregated series', () => {
           WHERE session_id = ?
         `,
       ).run(
-        startedAtMs + activeWatchedMs,
+        `${startedAtMs + activeWatchedMs}`,
         activeWatchedMs,
         activeWatchedMs,
         10,
@@ -687,8 +672,8 @@ test('getTrendsDashboard returns chart-ready aggregated series', () => {
       '名詞',
       null,
       null,
-      Math.floor(dayOneStart / 1000),
-      Math.floor(dayTwoStart / 1000),
+      String(Math.floor(dayOneStart / 1000)),
+      String(Math.floor(dayTwoStart / 1000)),
     );
 
     const dashboard = getTrendsDashboard(db, 'all', 'day');
@@ -743,18 +728,50 @@ test('getTrendsDashboard keeps local-midnight session buckets separate', () => {
       parseMetadataJson: null,
     });
 
-    const beforeMidnight = new Date(2026, 2, 1, 23, 30).getTime();
-    const afterMidnight = new Date(2026, 2, 2, 0, 30).getTime();
-    const firstSessionId = startSessionRecord(db, videoId, beforeMidnight).sessionId;
-    const secondSessionId = startSessionRecord(db, videoId, afterMidnight).sessionId;
+    const beforeMidnight = '1772436600000';
+    const afterMidnight = '1772440200000';
+    const firstSessionId = 1;
+    const secondSessionId = 2;
+    const insertSession = db.prepare(
+      `
+        INSERT INTO imm_sessions (
+          session_id,
+          session_uuid,
+          video_id,
+          started_at_ms,
+          status,
+          CREATED_DATE,
+          LAST_UPDATE_DATE
+        ) VALUES (?, ?, ?, ?, ?, ?, ?)
+      `,
+    );
+    insertSession.run(
+      firstSessionId,
+      '11111111-1111-1111-1111-111111111111',
+      videoId,
+      beforeMidnight,
+      1,
+      beforeMidnight,
+      beforeMidnight,
+    );
+    insertSession.run(
+      secondSessionId,
+      '22222222-2222-2222-2222-222222222222',
+      videoId,
+      afterMidnight,
+      1,
+      afterMidnight,
+      afterMidnight,
+    );
 
     for (const [sessionId, startedAtMs, tokensSeen, lookupCount] of [
       [firstSessionId, beforeMidnight, 100, 4],
       [secondSessionId, afterMidnight, 120, 6],
     ] as const) {
+      const endedAtMs = (BigInt(startedAtMs) + 60_000n).toString();
       stmts.telemetryInsertStmt.run(
         sessionId,
-        startedAtMs + 60_000,
+        endedAtMs,
         60_000,
         60_000,
         1,
@@ -767,8 +784,8 @@ test('getTrendsDashboard keeps local-midnight session buckets separate', () => {
         0,
         0,
         0,
-        startedAtMs + 60_000,
-        startedAtMs + 60_000,
+        endedAtMs,
+        endedAtMs,
       );
       db.prepare(
         `
@@ -787,7 +804,7 @@ test('getTrendsDashboard keeps local-midnight session buckets separate', () => {
         WHERE session_id = ?
         `,
       ).run(
-        startedAtMs + 60_000,
+        endedAtMs,
         60_000,
         60_000,
         1,
@@ -795,7 +812,7 @@ test('getTrendsDashboard keeps local-midnight session buckets separate', () => {
         lookupCount,
         lookupCount,
         lookupCount,
-        startedAtMs + 60_000,
+        endedAtMs,
         sessionId,
       );
     }
@@ -816,7 +833,7 @@ test('getTrendsDashboard keeps local-midnight session buckets separate', () => {
 test('getTrendsDashboard month grouping spans every touched calendar month and keeps progress monthly', () => {
   const dbPath = makeDbPath();
   const db = new Database(dbPath);
-  withMockDate(new Date(2026, 2, 1, 12, 0, 0), (RealDate) => {
+  withMockNowMs('1772395200000', () => {
     try {
       ensureSchema(db);
       const stmts = createTrackerPreparedStatements(db);
@@ -862,18 +879,50 @@ test('getTrendsDashboard month grouping spans every touched calendar month and k
         parseMetadataJson: null,
       });
 
-      const febStartedAtMs = new RealDate(2026, 1, 15, 20, 0, 0).getTime();
-      const marStartedAtMs = new RealDate(2026, 2, 1, 9, 0, 0).getTime();
-      const febSessionId = startSessionRecord(db, febVideoId, febStartedAtMs).sessionId;
-      const marSessionId = startSessionRecord(db, marVideoId, marStartedAtMs).sessionId;
+      const febStartedAtMs = '1771214400000';
+      const marStartedAtMs = '1772384400000';
+      const febSessionId = 1;
+      const marSessionId = 2;
+      const insertSession = db.prepare(
+        `
+          INSERT INTO imm_sessions (
+            session_id,
+            session_uuid,
+            video_id,
+            started_at_ms,
+            status,
+            CREATED_DATE,
+            LAST_UPDATE_DATE
+          ) VALUES (?, ?, ?, ?, ?, ?, ?)
+        `,
+      );
+      insertSession.run(
+        febSessionId,
+        '33333333-3333-3333-3333-333333333333',
+        febVideoId,
+        febStartedAtMs,
+        1,
+        febStartedAtMs,
+        febStartedAtMs,
+      );
+      insertSession.run(
+        marSessionId,
+        '44444444-4444-4444-4444-444444444444',
+        marVideoId,
+        marStartedAtMs,
+        1,
+        marStartedAtMs,
+        marStartedAtMs,
+      );
 
       for (const [sessionId, startedAtMs, tokensSeen, cardsMined, yomitanLookupCount] of [
         [febSessionId, febStartedAtMs, 100, 2, 3],
         [marSessionId, marStartedAtMs, 120, 4, 5],
       ] as const) {
+        const endedAtMs = (BigInt(startedAtMs) + 60_000n).toString();
         stmts.telemetryInsertStmt.run(
           sessionId,
-          startedAtMs + 60_000,
+          endedAtMs,
           30 * 60_000,
           30 * 60_000,
           4,
@@ -886,8 +935,8 @@ test('getTrendsDashboard month grouping spans every touched calendar month and k
           0,
           0,
           0,
-          startedAtMs + 60_000,
-          startedAtMs + 60_000,
+          endedAtMs,
+          endedAtMs,
         );
         db.prepare(
           `
@@ -907,7 +956,7 @@ test('getTrendsDashboard month grouping spans every touched calendar month and k
           WHERE session_id = ?
           `,
         ).run(
-          startedAtMs + 60_000,
+          endedAtMs,
           30 * 60_000,
           30 * 60_000,
           4,
@@ -916,7 +965,7 @@ test('getTrendsDashboard month grouping spans every touched calendar month and k
           yomitanLookupCount,
           yomitanLookupCount,
           yomitanLookupCount,
-          startedAtMs + 60_000,
+          endedAtMs,
           sessionId,
         );
       }
@@ -937,10 +986,8 @@ test('getTrendsDashboard month grouping spans every touched calendar month and k
       ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
     `,
     );
-    const febEpochDay = Math.floor(febStartedAtMs / 86_400_000);
-    const marEpochDay = Math.floor(marStartedAtMs / 86_400_000);
-    insertDailyRollup.run(febEpochDay, febVideoId, 1, 30, 4, 100, 2, febStartedAtMs, febStartedAtMs);
-    insertDailyRollup.run(marEpochDay, marVideoId, 1, 30, 4, 120, 4, marStartedAtMs, marStartedAtMs);
+    insertDailyRollup.run(20500, febVideoId, 1, 30, 4, 100, 2, febStartedAtMs, febStartedAtMs);
+    insertDailyRollup.run(20513, marVideoId, 1, 30, 4, 120, 4, marStartedAtMs, marStartedAtMs);
     insertMonthlyRollup.run(202602, febVideoId, 1, 30, 4, 100, 2, febStartedAtMs, febStartedAtMs);
     insertMonthlyRollup.run(202603, marVideoId, 1, 30, 4, 120, 4, marStartedAtMs, marStartedAtMs);
 
@@ -958,8 +1005,8 @@ test('getTrendsDashboard month grouping spans every touched calendar month and k
       '名詞',
       '',
       '',
-      Math.floor(febStartedAtMs / 1000),
-      Math.floor(febStartedAtMs / 1000),
+      (BigInt(febStartedAtMs) / 1000n).toString(),
+      (BigInt(febStartedAtMs) / 1000n).toString(),
       1,
     );
     db.prepare(
@@ -976,8 +1023,8 @@ test('getTrendsDashboard month grouping spans every touched calendar month and k
       '名詞',
       '',
       '',
-      Math.floor(marStartedAtMs / 1000),
-      Math.floor(marStartedAtMs / 1000),
+      (BigInt(marStartedAtMs) / 1000n).toString(),
+      (BigInt(marStartedAtMs) / 1000n).toString(),
       1,
     );
 
@@ -1077,7 +1124,7 @@ test('getQueryHints computes weekly new-word cutoff from calendar midnights', ()
   const dbPath = makeDbPath();
   const db = new Database(dbPath);
 
-  withMockDate(new Date(2026, 2, 15, 12, 0, 0), (RealDate) => {
+  withMockNowMs('1773601200000', () => {
     try {
       ensureSchema(db);
 
@@ -1088,12 +1135,8 @@ test('getQueryHints computes weekly new-word cutoff from calendar midnights', ()
         ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
         `,
       );
-      const justBeforeWeekBoundary = Math.floor(
-        new RealDate(2026, 2, 7, 23, 30, 0).getTime() / 1000,
-      );
-      const justAfterWeekBoundary = Math.floor(
-        new RealDate(2026, 2, 8, 0, 30, 0).getTime() / 1000,
-      );
+      const justBeforeWeekBoundary = 1_772_955_000;
+      const justAfterWeekBoundary = 1_772_958_600;
       insertWord.run(
         '境界前',
         '境界前',
@@ -1102,8 +1145,8 @@ test('getQueryHints computes weekly new-word cutoff from calendar midnights', ()
         '名詞',
         '',
         '',
-        justBeforeWeekBoundary,
-        justBeforeWeekBoundary,
+        String(justBeforeWeekBoundary),
+        String(justBeforeWeekBoundary),
         1,
       );
       insertWord.run(
@@ -1114,8 +1157,8 @@ test('getQueryHints computes weekly new-word cutoff from calendar midnights', ()
         '名詞',
         '',
         '',
-        justAfterWeekBoundary,
-        justAfterWeekBoundary,
+        String(justAfterWeekBoundary),
+        String(justAfterWeekBoundary),
         1,
       );
 
@@ -1134,38 +1177,70 @@ test('getQueryHints counts new words by distinct headword first-seen time', () =
 
   try {
     ensureSchema(db);
+    withMockNowMs('1773601200000', () => {
+      const todayStartSec = 1_773_558_000;
+      const oneHourAgo = todayStartSec + 3_600;
+      const twoDaysAgo = todayStartSec - 2 * 86_400;
 
-    const now = new Date();
-    const todayStartSec =
-      new Date(now.getFullYear(), now.getMonth(), now.getDate()).getTime() / 1000;
-    const oneHourAgo = todayStartSec + 3_600;
-    const twoDaysAgo = todayStartSec - 2 * 86_400;
+      db.prepare(
+        `
+        INSERT INTO imm_words (
+          headword, word, reading, part_of_speech, pos1, pos2, pos3, first_seen, last_seen, frequency
+        ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+        `,
+      ).run(
+        '知る',
+        '知った',
+        'しった',
+        'verb',
+        '動詞',
+        '',
+        '',
+        String(oneHourAgo),
+        String(oneHourAgo),
+        1,
+      );
+      db.prepare(
+        `
+        INSERT INTO imm_words (
+          headword, word, reading, part_of_speech, pos1, pos2, pos3, first_seen, last_seen, frequency
+        ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+        `,
+      ).run(
+        '知る',
+        '知っている',
+        'しっている',
+        'verb',
+        '動詞',
+        '',
+        '',
+        String(oneHourAgo),
+        String(oneHourAgo),
+        1,
+      );
+      db.prepare(
+        `
+        INSERT INTO imm_words (
+          headword, word, reading, part_of_speech, pos1, pos2, pos3, first_seen, last_seen, frequency
+        ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+        `,
+      ).run(
+        '猫',
+        '猫',
+        'ねこ',
+        'noun',
+        '名詞',
+        '',
+        '',
+        String(twoDaysAgo),
+        String(twoDaysAgo),
+        1,
+      );
 
-    db.prepare(
-      `
-      INSERT INTO imm_words (
-        headword, word, reading, part_of_speech, pos1, pos2, pos3, first_seen, last_seen, frequency
-      ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
-      `,
-    ).run('知る', '知った', 'しった', 'verb', '動詞', '', '', oneHourAgo, oneHourAgo, 1);
-    db.prepare(
-      `
-      INSERT INTO imm_words (
-        headword, word, reading, part_of_speech, pos1, pos2, pos3, first_seen, last_seen, frequency
-      ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
-      `,
-    ).run('知る', '知っている', 'しっている', 'verb', '動詞', '', '', oneHourAgo, oneHourAgo, 1);
-    db.prepare(
-      `
-      INSERT INTO imm_words (
-        headword, word, reading, part_of_speech, pos1, pos2, pos3, first_seen, last_seen, frequency
-      ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
-      `,
-    ).run('猫', '猫', 'ねこ', 'noun', '名詞', '', '', twoDaysAgo, twoDaysAgo, 1);
-
-    const hints = getQueryHints(db);
-    assert.equal(hints.newWordsToday, 1);
-    assert.equal(hints.newWordsThisWeek, 2);
+      const hints = getQueryHints(db);
+      assert.equal(hints.newWordsToday, 1);
+      assert.equal(hints.newWordsThisWeek, 2);
+    });
   } finally {
     db.close();
     cleanupDbPath(dbPath);
@@ -2020,7 +2095,7 @@ test('getSessionWordsByLine joins word occurrences through imm_words.id', () =>
   try {
     ensureSchema(db);
     const stmts = createTrackerPreparedStatements(db);
-    const startedAtMs = Date.UTC(2025, 0, 1, 12, 0, 0);
+    const startedAtMs = 1_735_732_800_000;
     const videoId = getOrCreateVideoRecord(db, '/tmp/session-words-by-line.mkv', {
       canonicalTitle: 'Episode',
       sourcePath: '/tmp/session-words-by-line.mkv',
diff --git a/src/core/services/immersion-tracker/lifetime.ts b/src/core/services/immersion-tracker/lifetime.ts
index 82c5c8ad..e0aac328 100644
--- a/src/core/services/immersion-tracker/lifetime.ts
+++ b/src/core/services/immersion-tracker/lifetime.ts
@@ -1,6 +1,7 @@
 import type { DatabaseSync } from './sqlite';
 import { finalizeSessionRecord } from './session';
 import { nowMs } from './time';
+import { toDbTimestamp } from './query-shared';
 import type { LifetimeRebuildSummary, SessionState } from './types';
 
 interface TelemetryRow {
@@ -41,8 +42,8 @@ interface LifetimeAnimeStateRow {
 interface RetainedSessionRow {
   sessionId: number;
   videoId: number;
-  startedAtMs: number;
-  endedAtMs: number;
+  startedAtMs: number | string;
+  endedAtMs: number | string;
   lastMediaMs: number | null;
   totalWatchedMs: number;
   activeWatchedMs: number;
@@ -65,25 +66,29 @@ function hasRetainedPriorSession(
   startedAtMs: number,
   currentSessionId: number,
 ): boolean {
-  return (
-    Number(
-      (
-        db
-          .prepare(
-            `
-            SELECT COUNT(*) AS count
-            FROM imm_sessions
-            WHERE video_id = ?
-              AND (
-                started_at_ms < ?
-                OR (started_at_ms = ? AND session_id < ?)
-              )
-            `,
+  const row = db
+    .prepare(
+      `
+      SELECT 1 AS found
+      FROM imm_sessions
+      WHERE video_id = ?
+        AND (
+          CAST(started_at_ms AS REAL) < CAST(? AS REAL)
+          OR (
+            CAST(started_at_ms AS REAL) = CAST(? AS REAL)
+            AND session_id < ?
           )
-          .get(videoId, startedAtMs, startedAtMs, currentSessionId) as ExistenceRow | null
-      )?.count ?? 0,
-    ) > 0
-  );
+        )
+      LIMIT 1
+    `,
+    )
+    .get(
+      videoId,
+      toDbTimestamp(startedAtMs),
+      toDbTimestamp(startedAtMs),
+      currentSessionId,
+    ) as { found: number } | null;
+  return Boolean(row);
 }
 
 function isFirstSessionForLocalDay(
@@ -91,23 +96,37 @@ function isFirstSessionForLocalDay(
   currentSessionId: number,
   startedAtMs: number,
 ): boolean {
-  return (
-    (
-      db
-        .prepare(
-          `
-      SELECT COUNT(*) AS count
+  const row = db
+    .prepare(
+      `
+      SELECT 1 AS found
       FROM imm_sessions
-      WHERE date(started_at_ms / 1000, 'unixepoch', 'localtime') = date(? / 1000, 'unixepoch', 'localtime')
+      WHERE session_id != ?
+        AND CAST(
+          julianday(CAST(started_at_ms AS REAL) / 1000, 'unixepoch', 'localtime') - 2440587.5
+          AS INTEGER
+        ) = CAST(
+          julianday(CAST(? AS REAL) / 1000, 'unixepoch', 'localtime') - 2440587.5
+          AS INTEGER
+        )
         AND (
-          started_at_ms < ?
-          OR (started_at_ms = ? AND session_id < ?)
+          CAST(started_at_ms AS REAL) < CAST(? AS REAL)
+          OR (
+            CAST(started_at_ms AS REAL) = CAST(? AS REAL)
+            AND session_id < ?
+          )
         )
-      `,
-        )
-        .get(startedAtMs, startedAtMs, startedAtMs, currentSessionId) as ExistenceRow | null
-    )?.count === 0
-  );
+      LIMIT 1
+    `,
+    )
+    .get(
+      currentSessionId,
+      toDbTimestamp(startedAtMs),
+      toDbTimestamp(startedAtMs),
+      toDbTimestamp(startedAtMs),
+      currentSessionId,
+    ) as { found: number } | null;
+  return !row;
 }
 
 function resetLifetimeSummaries(db: DatabaseSync, nowMs: number): void {
@@ -131,14 +150,14 @@ function resetLifetimeSummaries(db: DatabaseSync, nowMs: number): void {
       LAST_UPDATE_DATE = ?
     WHERE global_id = 1
     `,
-  ).run(nowMs, nowMs);
+    ).run(toDbTimestamp(nowMs), toDbTimestamp(nowMs));
 }
 
 function rebuildLifetimeSummariesInternal(
   db: DatabaseSync,
   rebuiltAtMs: number,
 ): LifetimeRebuildSummary {
-  const sessions = db
+  const rows = db
     .prepare(
       `
       SELECT
@@ -146,6 +165,7 @@ function rebuildLifetimeSummariesInternal(
         video_id AS videoId,
         started_at_ms AS startedAtMs,
         ended_at_ms AS endedAtMs,
+        ended_media_ms AS lastMediaMs,
         total_watched_ms AS totalWatchedMs,
         active_watched_ms AS activeWatchedMs,
         lines_seen AS linesSeen,
@@ -164,7 +184,19 @@ function rebuildLifetimeSummariesInternal(
       ORDER BY started_at_ms ASC, session_id ASC
       `,
     )
-    .all() as RetainedSessionRow[];
+    .all() as Array<
+    Omit<RetainedSessionRow, 'startedAtMs' | 'endedAtMs' | 'lastMediaMs'> & {
+      startedAtMs: number | string;
+      endedAtMs: number | string;
+      lastMediaMs: number | string | null;
+    }
+  >;
+  const sessions = rows.map((row) => ({
+    ...row,
+    startedAtMs: row.startedAtMs,
+    endedAtMs: row.endedAtMs,
+    lastMediaMs: row.lastMediaMs === null ? null : Number(row.lastMediaMs),
+  })) as RetainedSessionRow[];
 
   resetLifetimeSummaries(db, rebuiltAtMs);
   for (const session of sessions) {
@@ -181,9 +213,9 @@ function toRebuildSessionState(row: RetainedSessionRow): SessionState {
   return {
     sessionId: row.sessionId,
     videoId: row.videoId,
-    startedAtMs: row.startedAtMs,
+    startedAtMs: row.startedAtMs as number,
     currentLineIndex: 0,
-    lastWallClockMs: row.endedAtMs,
+    lastWallClockMs: row.endedAtMs as number,
     lastMediaMs: row.lastMediaMs,
     lastPauseStartMs: null,
     isPaused: false,
@@ -206,7 +238,7 @@ function toRebuildSessionState(row: RetainedSessionRow): SessionState {
 }
 
 function getRetainedStaleActiveSessions(db: DatabaseSync): RetainedSessionRow[] {
-  return db
+  const rows = db
     .prepare(
       `
       SELECT
@@ -241,20 +273,32 @@ function getRetainedStaleActiveSessions(db: DatabaseSync): RetainedSessionRow[]
       ORDER BY s.started_at_ms ASC, s.session_id ASC
       `,
     )
-    .all() as RetainedSessionRow[];
+    .all() as Array<
+    Omit<RetainedSessionRow, 'startedAtMs' | 'endedAtMs' | 'lastMediaMs'> & {
+      startedAtMs: number | string;
+      endedAtMs: number | string;
+      lastMediaMs: number | string | null;
+    }
+  >;
+  return rows.map((row) => ({
+    ...row,
+    startedAtMs: row.startedAtMs,
+    endedAtMs: row.endedAtMs,
+    lastMediaMs: row.lastMediaMs === null ? null : Number(row.lastMediaMs),
+  })) as RetainedSessionRow[];
 }
 
 function upsertLifetimeMedia(
   db: DatabaseSync,
   videoId: number,
-  nowMs: number,
+  nowMs: number | string,
   activeMs: number,
   cardsMined: number,
   linesSeen: number,
   tokensSeen: number,
   completed: number,
-  startedAtMs: number,
-  endedAtMs: number,
+  startedAtMs: number | string,
+  endedAtMs: number | string,
 ): void {
   db.prepare(
     `
@@ -310,15 +354,15 @@ function upsertLifetimeMedia(
 function upsertLifetimeAnime(
   db: DatabaseSync,
   animeId: number,
-  nowMs: number,
+  nowMs: number | string,
   activeMs: number,
   cardsMined: number,
   linesSeen: number,
   tokensSeen: number,
   episodesStartedDelta: number,
   episodesCompletedDelta: number,
-  startedAtMs: number,
-  endedAtMs: number,
+  startedAtMs: number | string,
+  endedAtMs: number | string,
 ): void {
   db.prepare(
     `
@@ -377,8 +421,9 @@ function upsertLifetimeAnime(
 export function applySessionLifetimeSummary(
   db: DatabaseSync,
   session: SessionState,
-  endedAtMs: number,
+  endedAtMs: number | string,
 ): void {
+  const updatedAtMs = toDbTimestamp(nowMs());
   const applyResult = db
     .prepare(
       `
@@ -393,7 +438,7 @@ export function applySessionLifetimeSummary(
       ON CONFLICT(session_id) DO NOTHING
       `,
     )
-    .run(session.sessionId, endedAtMs, nowMs(), nowMs());
+    .run(session.sessionId, endedAtMs, updatedAtMs, updatedAtMs);
 
   if ((applyResult.changes ?? 0) <= 0) {
     return;
@@ -468,7 +513,6 @@ export function applySessionLifetimeSummary(
       ? 1
       : 0;
 
-  const updatedAtMs = nowMs();
   db.prepare(
     `
     UPDATE imm_lifetime_global
diff --git a/src/core/services/immersion-tracker/maintenance.test.ts b/src/core/services/immersion-tracker/maintenance.test.ts
index cdb62258..8f68700c 100644
--- a/src/core/services/immersion-tracker/maintenance.test.ts
+++ b/src/core/services/immersion-tracker/maintenance.test.ts
@@ -11,6 +11,7 @@ import {
   toMonthKey,
 } from './maintenance';
 import { ensureSchema } from './storage';
+import { toDbTimestamp } from './query-shared';
 
 function makeDbPath(): string {
   const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'subminer-maintenance-test-'));
@@ -39,18 +40,18 @@ test('pruneRawRetention uses session retention separately from telemetry retenti
       INSERT INTO imm_videos (
         video_id, video_key, canonical_title, source_type, duration_ms, CREATED_DATE, LAST_UPDATE_DATE
       ) VALUES (
-        1, 'local:/tmp/video.mkv', 'Video', 1, 0, ${nowMs}, ${nowMs}
+        1, 'local:/tmp/video.mkv', 'Video', 1, 0, '${toDbTimestamp(nowMs)}', '${toDbTimestamp(nowMs)}'
       );
       INSERT INTO imm_sessions (
         session_id, session_uuid, video_id, started_at_ms, ended_at_ms, status, CREATED_DATE, LAST_UPDATE_DATE
       ) VALUES
-        (1, 'session-1', 1, ${staleEndedAtMs - 1_000}, ${staleEndedAtMs}, 2, ${staleEndedAtMs}, ${staleEndedAtMs}),
-        (2, 'session-2', 1, ${keptEndedAtMs - 1_000}, ${keptEndedAtMs}, 2, ${keptEndedAtMs}, ${keptEndedAtMs});
+        (1, 'session-1', 1, '${toDbTimestamp(staleEndedAtMs - 1_000)}', '${toDbTimestamp(staleEndedAtMs)}', 2, '${toDbTimestamp(staleEndedAtMs)}', '${toDbTimestamp(staleEndedAtMs)}'),
+        (2, 'session-2', 1, '${toDbTimestamp(keptEndedAtMs - 1_000)}', '${toDbTimestamp(keptEndedAtMs)}', 2, '${toDbTimestamp(keptEndedAtMs)}', '${toDbTimestamp(keptEndedAtMs)}');
       INSERT INTO imm_session_telemetry (
         session_id, sample_ms, total_watched_ms, active_watched_ms, CREATED_DATE, LAST_UPDATE_DATE
       ) VALUES
-        (1, ${nowMs - 200_000_000}, 0, 0, ${nowMs}, ${nowMs}),
-        (2, ${nowMs - 10_000_000}, 0, 0, ${nowMs}, ${nowMs});
+        (1, '${toDbTimestamp(nowMs - 200_000_000)}', 0, 0, '${toDbTimestamp(nowMs)}', '${toDbTimestamp(nowMs)}'),
+        (2, '${toDbTimestamp(nowMs - 10_000_000)}', 0, 0, '${toDbTimestamp(nowMs)}', '${toDbTimestamp(nowMs)}');
     `);
 
     const result = pruneRawRetention(db, nowMs, {
@@ -94,22 +95,22 @@ test('pruneRawRetention skips disabled retention windows', () => {
       INSERT INTO imm_videos (
         video_id, video_key, canonical_title, source_type, duration_ms, CREATED_DATE, LAST_UPDATE_DATE
       ) VALUES (
-        1, 'local:/tmp/video.mkv', 'Video', 1, 0, ${nowMs}, ${nowMs}
+        1, 'local:/tmp/video.mkv', 'Video', 1, 0, '${nowMs}', '${nowMs}'
       );
       INSERT INTO imm_sessions (
         session_id, session_uuid, video_id, started_at_ms, ended_at_ms, status, CREATED_DATE, LAST_UPDATE_DATE
       ) VALUES (
-        1, 'session-1', 1, ${nowMs - 1_000}, ${nowMs - 500}, 2, ${nowMs}, ${nowMs}
+        1, 'session-1', 1, '${nowMs - 1_000}', '${nowMs - 500}', 2, '${nowMs}', '${nowMs}'
       );
       INSERT INTO imm_session_telemetry (
         session_id, sample_ms, total_watched_ms, active_watched_ms, CREATED_DATE, LAST_UPDATE_DATE
       ) VALUES (
-        1, ${nowMs - 2_000}, 0, 0, ${nowMs}, ${nowMs}
+        1, '${nowMs - 2_000}', 0, 0, '${nowMs}', '${nowMs}'
       );
       INSERT INTO imm_session_events (
         session_id, event_type, ts_ms, payload_json, CREATED_DATE, LAST_UPDATE_DATE
       ) VALUES (
-        1, 1, ${nowMs - 3_000}, '{}', ${nowMs}, ${nowMs}
+        1, 1, '${nowMs - 3_000}', '{}', '${nowMs}', '${nowMs}'
       );
     `);
 
@@ -161,17 +162,17 @@ test('raw retention keeps rollups and rollup retention prunes them separately',
       INSERT INTO imm_videos (
         video_id, video_key, canonical_title, source_type, duration_ms, CREATED_DATE, LAST_UPDATE_DATE
       ) VALUES (
-        1, 'local:/tmp/video.mkv', 'Video', 1, 0, ${nowMs}, ${nowMs}
+        1, 'local:/tmp/video.mkv', 'Video', 1, 0, '${nowMs}', '${nowMs}'
       );
       INSERT INTO imm_sessions (
         session_id, session_uuid, video_id, started_at_ms, ended_at_ms, status, CREATED_DATE, LAST_UPDATE_DATE
       ) VALUES (
-        1, 'session-1', 1, ${nowMs - 200_000_000}, ${nowMs - 199_999_000}, 2, ${nowMs}, ${nowMs}
+        1, 'session-1', 1, '${nowMs - 200_000_000}', '${nowMs - 199_999_000}', 2, '${nowMs}', '${nowMs}'
       );
       INSERT INTO imm_session_telemetry (
         session_id, sample_ms, total_watched_ms, active_watched_ms, CREATED_DATE, LAST_UPDATE_DATE
       ) VALUES (
-        1, ${nowMs - 200_000_000}, 0, 0, ${nowMs}, ${nowMs}
+        1, '${nowMs - 200_000_000}', 0, 0, '${nowMs}', '${nowMs}'
       );
       INSERT INTO imm_daily_rollups (
         rollup_day, video_id, total_sessions, total_active_min, total_lines_seen,
@@ -183,7 +184,7 @@ test('raw retention keeps rollups and rollup retention prunes them separately',
         rollup_month, video_id, total_sessions, total_active_min, total_lines_seen,
         total_tokens_seen, total_cards, CREATED_DATE, LAST_UPDATE_DATE
       ) VALUES (
-        ${oldMonth}, 1, 1, 10, 1, 1, 1, ${nowMs}, ${nowMs}
+        ${oldMonth}, 1, 1, 10, 1, 1, 1, '${nowMs}', '${nowMs}'
       );
     `);
 
diff --git a/src/core/services/immersion-tracker/maintenance.ts b/src/core/services/immersion-tracker/maintenance.ts
index 1ed9bc9c..d225f0d2 100644
--- a/src/core/services/immersion-tracker/maintenance.ts
+++ b/src/core/services/immersion-tracker/maintenance.ts
@@ -1,13 +1,13 @@
 import type { DatabaseSync } from './sqlite';
 import { nowMs } from './time';
-import { toDbMs } from './query-shared';
+import { subtractDbTimestamp, toDbTimestamp } from './query-shared';
 
 const ROLLUP_STATE_KEY = 'last_rollup_sample_ms';
 const DAILY_MS = 86_400_000;
 const ZERO_ID = 0;
 
 interface RollupStateRow {
-  state_value: number;
+  state_value: string;
 }
 
 interface RollupGroupRow {
@@ -51,12 +51,25 @@ export function pruneRawRetention(
     eventsRetentionMs: number;
     telemetryRetentionMs: number;
     sessionsRetentionMs: number;
+    eventsRetentionDays?: number;
+    telemetryRetentionDays?: number;
+    sessionsRetentionDays?: number;
   },
 ): RawRetentionResult {
+  const resolveCutoff = (
+    retentionMs: number,
+    retentionDays: number | undefined,
+  ): string => {
+    if (retentionDays !== undefined) {
+      return subtractDbTimestamp(currentMs, BigInt(retentionDays) * 86_400_000n);
+    }
+    return subtractDbTimestamp(currentMs, retentionMs);
+  };
+
   const deletedSessionEvents = Number.isFinite(policy.eventsRetentionMs)
     ? (
         db.prepare(`DELETE FROM imm_session_events WHERE ts_ms < ?`).run(
-          toDbMs(currentMs - policy.eventsRetentionMs),
+          resolveCutoff(policy.eventsRetentionMs, policy.eventsRetentionDays),
         ) as { changes: number }
       ).changes
     : 0;
@@ -64,14 +77,18 @@ export function pruneRawRetention(
     ? (
         db
           .prepare(`DELETE FROM imm_session_telemetry WHERE sample_ms < ?`)
-          .run(toDbMs(currentMs - policy.telemetryRetentionMs)) as { changes: number }
+          .run(resolveCutoff(policy.telemetryRetentionMs, policy.telemetryRetentionDays)) as {
+          changes: number;
+        }
       ).changes
     : 0;
   const deletedEndedSessions = Number.isFinite(policy.sessionsRetentionMs)
     ? (
         db
           .prepare(`DELETE FROM imm_sessions WHERE ended_at_ms IS NOT NULL AND ended_at_ms < ?`)
-          .run(toDbMs(currentMs - policy.sessionsRetentionMs)) as { changes: number }
+          .run(resolveCutoff(policy.sessionsRetentionMs, policy.sessionsRetentionDays)) as {
+          changes: number;
+        }
       ).changes
     : 0;
 
@@ -115,14 +132,14 @@ export function pruneRollupRetention(
   };
 }
 
-function getLastRollupSampleMs(db: DatabaseSync): number {
+function getLastRollupSampleMs(db: DatabaseSync): string {
   const row = db
     .prepare(`SELECT state_value FROM imm_rollup_state WHERE state_key = ? LIMIT 1`)
     .get(ROLLUP_STATE_KEY) as unknown as RollupStateRow | null;
-  return row ? Number(row.state_value) : ZERO_ID;
+  return row ? row.state_value : String(ZERO_ID);
 }
 
-function setLastRollupSampleMs(db: DatabaseSync, sampleMs: number | bigint): void {
+function setLastRollupSampleMs(db: DatabaseSync, sampleMs: number | bigint | string): void {
   db.prepare(
     `INSERT INTO imm_rollup_state (state_key, state_value)
        VALUES (?, ?)
@@ -141,7 +158,7 @@ function resetRollups(db: DatabaseSync): void {
 function upsertDailyRollupsForGroups(
   db: DatabaseSync,
   groups: Array<{ rollupDay: number; videoId: number }>,
-  rollupNowMs: bigint,
+  rollupNowMs: number | string,
 ): void {
   if (groups.length === 0) {
     return;
@@ -217,7 +234,7 @@ function upsertDailyRollupsForGroups(
 function upsertMonthlyRollupsForGroups(
   db: DatabaseSync,
   groups: Array<{ rollupMonth: number; videoId: number }>,
-  rollupNowMs: bigint,
+  rollupNowMs: number | string,
 ): void {
   if (groups.length === 0) {
     return;
@@ -268,7 +285,7 @@ function upsertMonthlyRollupsForGroups(
 
 function getAffectedRollupGroups(
   db: DatabaseSync,
-  lastRollupSampleMs: number,
+  lastRollupSampleMs: number | string,
 ): Array<{ rollupDay: number; rollupMonth: number; videoId: number }> {
   return (
     db
@@ -321,7 +338,7 @@ export function runRollupMaintenance(db: DatabaseSync, forceRebuild = false): vo
     return;
   }
 
-  const rollupNowMs = toDbMs(nowMs());
+  const rollupNowMs = toDbTimestamp(nowMs());
   const lastRollupSampleMs = getLastRollupSampleMs(db);
 
   const maxSampleRow = db
@@ -356,7 +373,7 @@ export function runRollupMaintenance(db: DatabaseSync, forceRebuild = false): vo
   try {
     upsertDailyRollupsForGroups(db, dailyGroups, rollupNowMs);
     upsertMonthlyRollupsForGroups(db, monthlyGroups, rollupNowMs);
-    setLastRollupSampleMs(db, toDbMs(maxSampleRow.maxSampleMs ?? ZERO_ID));
+    setLastRollupSampleMs(db, toDbTimestamp(maxSampleRow.maxSampleMs ?? ZERO_ID));
     db.exec('COMMIT');
   } catch (error) {
     db.exec('ROLLBACK');
@@ -365,7 +382,7 @@ export function runRollupMaintenance(db: DatabaseSync, forceRebuild = false): vo
 }
 
 export function rebuildRollupsInTransaction(db: DatabaseSync): void {
-  const rollupNowMs = toDbMs(nowMs());
+  const rollupNowMs = toDbTimestamp(nowMs());
   const maxSampleRow = db
     .prepare('SELECT MAX(sample_ms) AS maxSampleMs FROM imm_session_telemetry')
     .get() as unknown as RollupTelemetryResult | null;
@@ -377,7 +394,7 @@ export function rebuildRollupsInTransaction(db: DatabaseSync): void {
 
   const affectedGroups = getAffectedRollupGroups(db, ZERO_ID);
   if (affectedGroups.length === 0) {
-    setLastRollupSampleMs(db, toDbMs(maxSampleRow.maxSampleMs ?? ZERO_ID));
+    setLastRollupSampleMs(db, toDbTimestamp(maxSampleRow.maxSampleMs ?? ZERO_ID));
     return;
   }
 
@@ -396,7 +413,7 @@ export function rebuildRollupsInTransaction(db: DatabaseSync): void {
 
   upsertDailyRollupsForGroups(db, dailyGroups, rollupNowMs);
   upsertMonthlyRollupsForGroups(db, monthlyGroups, rollupNowMs);
-  setLastRollupSampleMs(db, toDbMs(maxSampleRow.maxSampleMs ?? ZERO_ID));
+  setLastRollupSampleMs(db, toDbTimestamp(maxSampleRow.maxSampleMs ?? ZERO_ID));
 }
 
 export function runOptimizeMaintenance(db: DatabaseSync): void {
diff --git a/src/core/services/immersion-tracker/query-lexical.ts b/src/core/services/immersion-tracker/query-lexical.ts
index 004a7139..5e6ac68d 100644
--- a/src/core/services/immersion-tracker/query-lexical.ts
+++ b/src/core/services/immersion-tracker/query-lexical.ts
@@ -12,6 +12,7 @@ import type {
   WordDetailRow,
   WordOccurrenceRow,
 } from './types';
+import { fromDbTimestamp } from './query-shared';
 
 export function getVocabularyStats(
   db: DatabaseSync,
@@ -134,7 +135,11 @@ export function getSessionEvents(
       SELECT event_type AS eventType, ts_ms AS tsMs, payload_json AS payload
       FROM imm_session_events WHERE session_id = ? ORDER BY ts_ms ASC LIMIT ?
     `);
-    return stmt.all(sessionId, limit) as SessionEventRow[];
+    const rows = stmt.all(sessionId, limit) as Array<SessionEventRow & { tsMs: number | string }>;
+    return rows.map((row) => ({
+      ...row,
+      tsMs: fromDbTimestamp(row.tsMs) ?? 0,
+    }));
   }
 
   const placeholders = eventTypes.map(() => '?').join(', ');
@@ -145,7 +150,13 @@ export function getSessionEvents(
     ORDER BY ts_ms ASC
     LIMIT ?
   `);
-  return stmt.all(sessionId, ...eventTypes, limit) as SessionEventRow[];
+  const rows = stmt.all(sessionId, ...eventTypes, limit) as Array<SessionEventRow & {
+    tsMs: number | string;
+  }>;
+  return rows.map((row) => ({
+    ...row,
+    tsMs: fromDbTimestamp(row.tsMs) ?? 0,
+  }));
 }
 
 export function getWordDetail(db: DatabaseSync, wordId: number): WordDetailRow | null {
diff --git a/src/core/services/immersion-tracker/query-library.ts b/src/core/services/immersion-tracker/query-library.ts
index cd03d6b6..13df7d1d 100644
--- a/src/core/services/immersion-tracker/query-library.ts
+++ b/src/core/services/immersion-tracker/query-library.ts
@@ -16,10 +16,10 @@ import type {
   StreakCalendarRow,
   WatchTimePerAnimeRow,
 } from './types';
-import { ACTIVE_SESSION_METRICS_CTE, resolvedCoverBlobExpr } from './query-shared';
+import { ACTIVE_SESSION_METRICS_CTE, fromDbTimestamp, resolvedCoverBlobExpr } from './query-shared';
 
 export function getAnimeLibrary(db: DatabaseSync): AnimeLibraryRow[] {
-  return db
+  const rows = db
     .prepare(
       `
     SELECT
@@ -40,11 +40,15 @@ export function getAnimeLibrary(db: DatabaseSync): AnimeLibraryRow[] {
     ORDER BY totalActiveMs DESC, lm.last_watched_ms DESC, canonicalTitle ASC
   `,
     )
-    .all() as unknown as AnimeLibraryRow[];
+    .all() as Array<AnimeLibraryRow & { lastWatchedMs: number | string }>;
+  return rows.map((row) => ({
+    ...row,
+    lastWatchedMs: fromDbTimestamp(row.lastWatchedMs) ?? 0,
+  }));
 }
 
 export function getAnimeDetail(db: DatabaseSync, animeId: number): AnimeDetailRow | null {
-  return db
+  const row = db
     .prepare(
       `
     ${ACTIVE_SESSION_METRICS_CTE}
@@ -75,7 +79,13 @@ export function getAnimeDetail(db: DatabaseSync, animeId: number): AnimeDetailRo
     GROUP BY a.anime_id
   `,
     )
-    .get(animeId) as unknown as AnimeDetailRow | null;
+    .get(animeId) as (AnimeDetailRow & { lastWatchedMs: number | string }) | null;
+  return row
+    ? {
+        ...row,
+        lastWatchedMs: fromDbTimestamp(row.lastWatchedMs) ?? 0,
+      }
+    : null;
 }
 
 export function getAnimeAnilistEntries(db: DatabaseSync, animeId: number): AnimeAnilistEntryRow[] {
@@ -98,7 +108,7 @@ export function getAnimeAnilistEntries(db: DatabaseSync, animeId: number): Anime
 }
 
 export function getAnimeEpisodes(db: DatabaseSync, animeId: number): AnimeEpisodeRow[] {
-  return db
+  const rows = db
     .prepare(
       `
     ${ACTIVE_SESSION_METRICS_CTE}
@@ -168,11 +178,21 @@ export function getAnimeEpisodes(db: DatabaseSync, animeId: number): AnimeEpisod
       v.video_id ASC
   `,
     )
-    .all(animeId) as unknown as AnimeEpisodeRow[];
+    .all(animeId) as Array<
+    AnimeEpisodeRow & {
+      endedMediaMs: number | string | null;
+      lastWatchedMs: number | string;
+    }
+  >;
+  return rows.map((row) => ({
+    ...row,
+    endedMediaMs: fromDbTimestamp(row.endedMediaMs),
+    lastWatchedMs: fromDbTimestamp(row.lastWatchedMs) ?? 0,
+  }));
 }
 
 export function getMediaLibrary(db: DatabaseSync): MediaLibraryRow[] {
-  return db
+  const rows = db
     .prepare(
       `
     SELECT
@@ -205,7 +225,11 @@ export function getMediaLibrary(db: DatabaseSync): MediaLibraryRow[] {
     ORDER BY lm.last_watched_ms DESC
   `,
     )
-    .all() as unknown as MediaLibraryRow[];
+    .all() as Array<MediaLibraryRow & { lastWatchedMs: number | string }>;
+  return rows.map((row) => ({
+    ...row,
+    lastWatchedMs: fromDbTimestamp(row.lastWatchedMs) ?? 0,
+  }));
 }
 
 export function getMediaDetail(db: DatabaseSync, videoId: number): MediaDetailRow | null {
@@ -253,7 +277,7 @@ export function getMediaSessions(
   videoId: number,
   limit = 100,
 ): SessionSummaryQueryRow[] {
-  return db
+  const rows = db
     .prepare(
       `
     ${ACTIVE_SESSION_METRICS_CTE}
@@ -279,7 +303,17 @@ export function getMediaSessions(
     LIMIT ?
   `,
     )
-    .all(videoId, limit) as unknown as SessionSummaryQueryRow[];
+    .all(videoId, limit) as Array<
+    SessionSummaryQueryRow & {
+      startedAtMs: number | string;
+      endedAtMs: number | string | null;
+    }
+  >;
+  return rows.map((row) => ({
+    ...row,
+    startedAtMs: fromDbTimestamp(row.startedAtMs) ?? 0,
+    endedAtMs: fromDbTimestamp(row.endedAtMs),
+  }));
 }
 
 export function getMediaDailyRollups(
@@ -351,7 +385,7 @@ export function getAnimeDailyRollups(
 
 export function getAnimeCoverArt(db: DatabaseSync, animeId: number): MediaArtRow | null {
   const resolvedCoverBlob = resolvedCoverBlobExpr('a', 'cab');
-  return db
+  const row = db
     .prepare(
       `
     SELECT
@@ -372,12 +406,18 @@ export function getAnimeCoverArt(db: DatabaseSync, animeId: number): MediaArtRow
     LIMIT 1
   `,
     )
-    .get(animeId) as unknown as MediaArtRow | null;
+    .get(animeId) as (MediaArtRow & { fetchedAtMs: number | string }) | null;
+  return row
+    ? {
+        ...row,
+        fetchedAtMs: fromDbTimestamp(row.fetchedAtMs) ?? 0,
+      }
+    : null;
 }
 
 export function getCoverArt(db: DatabaseSync, videoId: number): MediaArtRow | null {
   const resolvedCoverBlob = resolvedCoverBlobExpr('a', 'cab');
-  return db
+  const row = db
     .prepare(
       `
     SELECT
@@ -394,7 +434,13 @@ export function getCoverArt(db: DatabaseSync, videoId: number): MediaArtRow | nu
     WHERE a.video_id = ?
   `,
     )
-    .get(videoId) as unknown as MediaArtRow | null;
+    .get(videoId) as (MediaArtRow & { fetchedAtMs: number | string }) | null;
+  return row
+    ? {
+        ...row,
+        fetchedAtMs: fromDbTimestamp(row.fetchedAtMs) ?? 0,
+      }
+    : null;
 }
 
 export function getStreakCalendar(db: DatabaseSync, days = 90): StreakCalendarRow[] {
@@ -510,7 +556,7 @@ export function getEpisodeWords(db: DatabaseSync, videoId: number, limit = 50):
 }
 
 export function getEpisodeSessions(db: DatabaseSync, videoId: number): SessionSummaryQueryRow[] {
-  return db
+  const rows = db
     .prepare(
       `
     ${ACTIVE_SESSION_METRICS_CTE}
@@ -533,7 +579,17 @@ export function getEpisodeSessions(db: DatabaseSync, videoId: number): SessionSu
     ORDER BY s.started_at_ms DESC
   `,
     )
-    .all(videoId) as SessionSummaryQueryRow[];
+    .all(videoId) as Array<
+    SessionSummaryQueryRow & {
+      startedAtMs: number | string;
+      endedAtMs: number | string | null;
+    }
+  >;
+  return rows.map((row) => ({
+    ...row,
+    startedAtMs: fromDbTimestamp(row.startedAtMs) ?? 0,
+    endedAtMs: fromDbTimestamp(row.endedAtMs),
+  }));
 }
 
 export function getEpisodeCardEvents(db: DatabaseSync, videoId: number): EpisodeCardEventRow[] {
@@ -552,7 +608,7 @@ export function getEpisodeCardEvents(db: DatabaseSync, videoId: number): Episode
     .all(videoId) as Array<{
     eventId: number;
     sessionId: number;
-    tsMs: number;
+    tsMs: number | string;
     cardsDelta: number;
     payloadJson: string | null;
   }>;
@@ -568,7 +624,7 @@ export function getEpisodeCardEvents(db: DatabaseSync, videoId: number): Episode
     return {
       eventId: row.eventId,
       sessionId: row.sessionId,
-      tsMs: row.tsMs,
+      tsMs: fromDbTimestamp(row.tsMs) ?? 0,
       cardsDelta: row.cardsDelta,
       noteIds,
     };
diff --git a/src/core/services/immersion-tracker/query-maintenance.ts b/src/core/services/immersion-tracker/query-maintenance.ts
index 022386fe..00b687c2 100644
--- a/src/core/services/immersion-tracker/query-maintenance.ts
+++ b/src/core/services/immersion-tracker/query-maintenance.ts
@@ -17,6 +17,7 @@ import {
   getAffectedWordIdsForVideo,
   refreshLexicalAggregates,
   toDbMs,
+  toDbTimestamp,
 } from './query-shared';
 
 type CleanupVocabularyRow = {
@@ -351,7 +352,7 @@ export function upsertCoverArt(
     )
     .get(videoId) as { coverBlobHash: string | null } | undefined;
   const sharedCoverBlobHash = findSharedCoverBlobHash(db, videoId, art.anilistId, art.coverUrl);
-  const fetchedAtMs = toDbMs(nowMs());
+  const fetchedAtMs = toDbTimestamp(nowMs());
   const coverBlob = normalizeCoverBlobBytes(art.coverBlob);
   const computedCoverBlobHash =
     coverBlob && coverBlob.length > 0
@@ -444,7 +445,7 @@ export function updateAnimeAnilistInfo(
     info.titleEnglish,
     info.titleNative,
     info.episodesTotal,
-    toDbMs(nowMs()),
+    toDbTimestamp(nowMs()),
     row.anime_id,
   );
 }
@@ -452,7 +453,7 @@ export function updateAnimeAnilistInfo(
 export function markVideoWatched(db: DatabaseSync, videoId: number, watched: boolean): void {
   db.prepare('UPDATE imm_videos SET watched = ?, LAST_UPDATE_DATE = ? WHERE video_id = ?').run(
     watched ? 1 : 0,
-    toDbMs(nowMs()),
+    toDbTimestamp(nowMs()),
     videoId,
   );
 }
diff --git a/src/core/services/immersion-tracker/query-sessions.ts b/src/core/services/immersion-tracker/query-sessions.ts
index 50224bd8..2d068656 100644
--- a/src/core/services/immersion-tracker/query-sessions.ts
+++ b/src/core/services/immersion-tracker/query-sessions.ts
@@ -1,11 +1,17 @@
 import type { DatabaseSync } from './sqlite';
-import { nowMs } from './time';
 import type {
   ImmersionSessionRollupRow,
   SessionSummaryQueryRow,
   SessionTimelineRow,
 } from './types';
-import { ACTIVE_SESSION_METRICS_CTE } from './query-shared';
+import {
+  ACTIVE_SESSION_METRICS_CTE,
+  currentDbTimestamp,
+  fromDbTimestamp,
+  getLocalEpochDay,
+  getShiftedLocalDaySec,
+  toDbTimestamp,
+} from './query-shared';
 
 export function getSessionSummaries(db: DatabaseSync, limit = 50): SessionSummaryQueryRow[] {
   const prepared = db.prepare(`
@@ -33,7 +39,15 @@ export function getSessionSummaries(db: DatabaseSync, limit = 50): SessionSummar
     ORDER BY s.started_at_ms DESC
     LIMIT ?
   `);
-  return prepared.all(limit) as unknown as SessionSummaryQueryRow[];
+  const rows = prepared.all(limit) as Array<SessionSummaryQueryRow & {
+    startedAtMs: number | string;
+    endedAtMs: number | string | null;
+  }>;
+  return rows.map((row) => ({
+    ...row,
+    startedAtMs: fromDbTimestamp(row.startedAtMs) ?? 0,
+    endedAtMs: fromDbTimestamp(row.endedAtMs),
+  }));
 }
 
 export function getSessionTimeline(
@@ -55,11 +69,23 @@ export function getSessionTimeline(
   `;
 
   if (limit === undefined) {
-    return db.prepare(select).all(sessionId) as unknown as SessionTimelineRow[];
+    const rows = db.prepare(select).all(sessionId) as Array<SessionTimelineRow & {
+      sampleMs: number | string;
+    }>;
+    return rows.map((row) => ({
+      ...row,
+      sampleMs: fromDbTimestamp(row.sampleMs) ?? 0,
+    }));
   }
-  return db
+  const rows = db
     .prepare(`${select}\n    LIMIT ?`)
-    .all(sessionId, limit) as unknown as SessionTimelineRow[];
+    .all(sessionId, limit) as Array<SessionTimelineRow & {
+    sampleMs: number | string;
+  }>;
+  return rows.map((row) => ({
+    ...row,
+    sampleMs: fromDbTimestamp(row.sampleMs) ?? 0,
+  }));
 }
 
 /** Returns all distinct headwords in the vocabulary table (global). */
@@ -129,35 +155,50 @@ export function getSessionWordsByLine(
 }
 
 function getNewWordCounts(db: DatabaseSync): { newWordsToday: number; newWordsThisWeek: number } {
-  const now = new Date();
-  const todayStartSec = new Date(now.getFullYear(), now.getMonth(), now.getDate()).getTime() / 1000;
-  const weekAgoSec =
-    new Date(now.getFullYear(), now.getMonth(), now.getDate() - 7).getTime() / 1000;
+  const currentTimestamp = currentDbTimestamp();
+  const todayStartSec = getShiftedLocalDaySec(db, currentTimestamp, 0);
+  const weekAgoSec = getShiftedLocalDaySec(db, currentTimestamp, -7);
 
-  const row = db
+  const rows = db
     .prepare(
       `
-    WITH headword_first_seen AS (
-      SELECT
-        headword,
-        MIN(first_seen) AS first_seen
-      FROM imm_words
-      WHERE first_seen IS NOT NULL
-        AND headword IS NOT NULL
-        AND headword != ''
-      GROUP BY headword
-    )
     SELECT
-      COALESCE(SUM(CASE WHEN first_seen >= ? THEN 1 ELSE 0 END), 0) AS today,
-      COALESCE(SUM(CASE WHEN first_seen >= ? THEN 1 ELSE 0 END), 0) AS week
-    FROM headword_first_seen
+      headword,
+      first_seen AS firstSeen
+    FROM imm_words
+    WHERE first_seen IS NOT NULL
+      AND headword IS NOT NULL
+      AND headword != ''
   `,
     )
-    .get(todayStartSec, weekAgoSec) as { today: number; week: number } | null;
+    .all() as Array<{ headword: string; firstSeen: number | string }>;
+
+  const firstSeenByHeadword = new Map<string, number>();
+  for (const row of rows) {
+    const firstSeen = Number(row.firstSeen);
+    if (!Number.isFinite(firstSeen)) {
+      continue;
+    }
+    const previous = firstSeenByHeadword.get(row.headword);
+    if (previous === undefined || firstSeen < previous) {
+      firstSeenByHeadword.set(row.headword, firstSeen);
+    }
+  }
+
+  let today = 0;
+  let week = 0;
+  for (const firstSeen of firstSeenByHeadword.values()) {
+    if (firstSeen >= todayStartSec) {
+      today += 1;
+    }
+    if (firstSeen >= weekAgoSec) {
+      week += 1;
+    }
+  }
 
   return {
-    newWordsToday: Number(row?.today ?? 0),
-    newWordsThisWeek: Number(row?.week ?? 0),
+    newWordsToday: today,
+    newWordsThisWeek: week,
   };
 }
 
@@ -203,10 +244,8 @@ export function getQueryHints(db: DatabaseSync): {
     animeCompleted: number;
   } | null;
 
-  const now = new Date();
-  const todayLocal = Math.floor(
-    new Date(now.getFullYear(), now.getMonth(), now.getDate()).getTime() / 86_400_000,
-  );
+  const currentTimestamp = currentDbTimestamp();
+  const todayLocal = getLocalEpochDay(db, currentTimestamp);
 
   const episodesToday =
     (
@@ -215,13 +254,16 @@ export function getQueryHints(db: DatabaseSync): {
           `
     SELECT COUNT(DISTINCT s.video_id) AS count
     FROM imm_sessions s
-    WHERE CAST(julianday(s.started_at_ms / 1000, 'unixepoch', 'localtime') - 2440587.5 AS INTEGER) = ?
+    WHERE CAST(
+      julianday(CAST(s.started_at_ms AS REAL) / 1000, 'unixepoch', 'localtime') - 2440587.5
+      AS INTEGER
+    ) = ?
   `,
         )
         .get(todayLocal) as { count: number }
     )?.count ?? 0;
 
-  const thirtyDaysAgoMs = nowMs() - 30 * 86400000;
+  const thirtyDaysAgoMs = getShiftedLocalDaySec(db, currentTimestamp, -30).toString() + '000';
   const activeAnimeCount =
     (
       db
diff --git a/src/core/services/immersion-tracker/query-shared.ts b/src/core/services/immersion-tracker/query-shared.ts
index c5d8312b..2634ce6e 100644
--- a/src/core/services/immersion-tracker/query-shared.ts
+++ b/src/core/services/immersion-tracker/query-shared.ts
@@ -1,4 +1,5 @@
 import type { DatabaseSync } from './sqlite';
+import { nowMs } from './time';
 
 export const ACTIVE_SESSION_METRICS_CTE = `
   WITH active_session_metrics AS (
@@ -280,3 +281,213 @@ export function toDbMs(ms: number | bigint): bigint {
   }
   return BigInt(Math.trunc(ms));
 }
+
+function normalizeTimestampString(value: string): string {
+  const trimmed = value.trim();
+  if (!trimmed) {
+    throw new TypeError(`Invalid database timestamp: ${value}`);
+  }
+
+  const integerLike = /^(-?)(\d+)(?:\.0+)?$/.exec(trimmed);
+  if (integerLike) {
+    const sign = integerLike[1] ?? '';
+    const digits = (integerLike[2] ?? '0').replace(/^0+(?=\d)/, '');
+    return `${sign}${digits || '0'}`;
+  }
+
+  const parsed = Number(trimmed);
+  if (!Number.isFinite(parsed)) {
+    throw new TypeError(`Invalid database timestamp: ${value}`);
+  }
+  return JSON.stringify(Math.trunc(parsed));
+}
+
+export function toDbTimestamp(ms: number | bigint | string): string {
+  const normalizeParsed = (parsed: number): string => JSON.stringify(Math.trunc(parsed));
+
+  if (typeof ms === 'bigint') {
+    return ms.toString();
+  }
+  if (typeof ms === 'string') {
+    return normalizeTimestampString(ms);
+  }
+  if (!Number.isFinite(ms)) {
+    throw new TypeError(`Invalid database timestamp: ${ms}`);
+  }
+  return normalizeParsed(ms);
+}
+
+export function currentDbTimestamp(): string {
+  const testNowMs = globalThis.__subminerTestNowMs;
+  if (typeof testNowMs === 'string') {
+    return normalizeTimestampString(testNowMs);
+  }
+  if (typeof testNowMs === 'number' && Number.isFinite(testNowMs)) {
+    return toDbTimestamp(testNowMs);
+  }
+  return toDbTimestamp(nowMs());
+}
+
+export function subtractDbTimestamp(
+  timestampMs: number | bigint | string,
+  deltaMs: number | bigint,
+): string {
+  return (BigInt(toDbTimestamp(timestampMs)) - BigInt(deltaMs)).toString();
+}
+
+export function fromDbTimestamp(ms: number | bigint | string | null | undefined): number | null {
+  if (ms === null || ms === undefined) {
+    return null;
+  }
+  if (typeof ms === 'number') {
+    return ms;
+  }
+  if (typeof ms === 'bigint') {
+    return Number(ms);
+  }
+  return Number(ms);
+}
+
+function getNumericCalendarValue(
+  db: DatabaseSync,
+  sql: string,
+  timestampMs: number | bigint | string,
+): number {
+  const row = db.prepare(sql).get(toDbTimestamp(timestampMs)) as
+    | { value: number | string | null }
+    | undefined;
+  return Number(row?.value ?? 0);
+}
+
+export function getLocalEpochDay(
+  db: DatabaseSync,
+  timestampMs: number | bigint | string,
+): number {
+  return getNumericCalendarValue(
+    db,
+    `
+      SELECT CAST(
+        julianday(CAST(? AS REAL) / 1000, 'unixepoch', 'localtime') - 2440587.5
+        AS INTEGER
+      ) AS value
+    `,
+    timestampMs,
+  );
+}
+
+export function getLocalMonthKey(
+  db: DatabaseSync,
+  timestampMs: number | bigint | string,
+): number {
+  return getNumericCalendarValue(
+    db,
+    `
+      SELECT CAST(
+        strftime('%Y%m', CAST(? AS REAL) / 1000, 'unixepoch', 'localtime')
+        AS INTEGER
+      ) AS value
+    `,
+    timestampMs,
+  );
+}
+
+export function getLocalDayOfWeek(
+  db: DatabaseSync,
+  timestampMs: number | bigint | string,
+): number {
+  return getNumericCalendarValue(
+    db,
+    `
+      SELECT CAST(
+        strftime('%w', CAST(? AS REAL) / 1000, 'unixepoch', 'localtime')
+        AS INTEGER
+      ) AS value
+    `,
+    timestampMs,
+  );
+}
+
+export function getLocalHourOfDay(
+  db: DatabaseSync,
+  timestampMs: number | bigint | string,
+): number {
+  return getNumericCalendarValue(
+    db,
+    `
+      SELECT CAST(
+        strftime('%H', CAST(? AS REAL) / 1000, 'unixepoch', 'localtime')
+        AS INTEGER
+      ) AS value
+    `,
+    timestampMs,
+  );
+}
+
+export function getStartOfLocalDaySec(
+  db: DatabaseSync,
+  timestampMs: number | bigint | string,
+): number {
+  return getNumericCalendarValue(
+    db,
+    `
+      SELECT CAST(
+        strftime(
+          '%s',
+          CAST(? AS REAL) / 1000,
+          'unixepoch',
+          'localtime',
+          'start of day',
+          'utc'
+        ) AS INTEGER
+      ) AS value
+    `,
+    timestampMs,
+  );
+}
+
+export function getStartOfLocalDayTimestamp(
+  db: DatabaseSync,
+  timestampMs: number | bigint | string,
+): string {
+  return `${getStartOfLocalDaySec(db, timestampMs)}000`;
+}
+
+export function getShiftedLocalDayTimestamp(
+  db: DatabaseSync,
+  timestampMs: number | bigint | string,
+  dayOffset: number,
+): string {
+  const normalizedDayOffset = Math.trunc(dayOffset);
+  const modifier = normalizedDayOffset >= 0 ? `+${normalizedDayOffset} days` : `${normalizedDayOffset} days`;
+  const row = db
+    .prepare(
+      `
+        SELECT strftime(
+          '%s',
+          CAST(? AS REAL) / 1000,
+          'unixepoch',
+          'localtime',
+          'start of day',
+          '${modifier}',
+          'utc'
+        ) AS value
+      `,
+    )
+    .get(toDbTimestamp(timestampMs)) as { value: string | number | null } | undefined;
+  return `${row?.value ?? '0'}000`;
+}
+
+export function getShiftedLocalDaySec(
+  db: DatabaseSync,
+  timestampMs: number | bigint | string,
+  dayOffset: number,
+): number {
+  return Number(BigInt(getShiftedLocalDayTimestamp(db, timestampMs, dayOffset)) / 1000n);
+}
+
+export function getStartOfLocalDayMs(
+  db: DatabaseSync,
+  timestampMs: number | bigint | string,
+): number {
+  return getStartOfLocalDaySec(db, timestampMs) * 1000;
+}
diff --git a/src/core/services/immersion-tracker/query-trends.ts b/src/core/services/immersion-tracker/query-trends.ts
index c72fae4f..4e7d2dcb 100644
--- a/src/core/services/immersion-tracker/query-trends.ts
+++ b/src/core/services/immersion-tracker/query-trends.ts
@@ -1,6 +1,16 @@
 import type { DatabaseSync } from './sqlite';
 import type { ImmersionSessionRollupRow } from './types';
-import { ACTIVE_SESSION_METRICS_CTE, makePlaceholders } from './query-shared';
+import {
+  ACTIVE_SESSION_METRICS_CTE,
+  currentDbTimestamp,
+  getLocalDayOfWeek,
+  getLocalEpochDay,
+  getLocalHourOfDay,
+  getLocalMonthKey,
+  getShiftedLocalDayTimestamp,
+  makePlaceholders,
+  toDbTimestamp,
+} from './query-shared';
 import { getDailyRollups, getMonthlyRollups } from './query-sessions';
 
 type TrendRange = '7d' | '30d' | '90d' | 'all';
@@ -19,6 +29,10 @@ interface TrendPerAnimePoint {
 
 interface TrendSessionMetricRow {
   startedAtMs: number;
+  epochDay: number;
+  monthKey: number;
+  dayOfWeek: number;
+  hourOfDay: number;
   videoId: number | null;
   canonicalTitle: string | null;
   animeTitle: string | null;
@@ -73,64 +87,64 @@ const TREND_DAY_LIMITS: Record<Exclude<TrendRange, 'all'>, number> = {
   '90d': 90,
 };
 
+const MONTH_NAMES = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];
+
 const DAY_NAMES = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'];
 
 function getTrendDayLimit(range: TrendRange): number {
   return range === 'all' ? 365 : TREND_DAY_LIMITS[range];
 }
 
-function getTrendMonthlyLimit(range: TrendRange): number {
+function getTrendMonthlyLimit(db: DatabaseSync, range: TrendRange): number {
   if (range === 'all') {
     return 120;
   }
-  const now = new Date();
-  const cutoff = new Date(
-    now.getFullYear(),
-    now.getMonth(),
-    now.getDate() - (TREND_DAY_LIMITS[range] - 1),
-  );
-  return Math.max(1, (now.getFullYear() - cutoff.getFullYear()) * 12 + now.getMonth() - cutoff.getMonth() + 1);
+  const currentTimestamp = currentDbTimestamp();
+  const todayStartMs = getShiftedLocalDayTimestamp(db, currentTimestamp, 0);
+  const cutoffMs = getShiftedLocalDayTimestamp(db, currentTimestamp, -(TREND_DAY_LIMITS[range] - 1));
+  const currentMonthKey = getLocalMonthKey(db, todayStartMs);
+  const cutoffMonthKey = getLocalMonthKey(db, cutoffMs);
+  const currentYear = Math.floor(currentMonthKey / 100);
+  const currentMonth = currentMonthKey % 100;
+  const cutoffYear = Math.floor(cutoffMonthKey / 100);
+  const cutoffMonth = cutoffMonthKey % 100;
+  return Math.max(1, (currentYear - cutoffYear) * 12 + currentMonth - cutoffMonth + 1);
 }
 
-function getTrendCutoffMs(range: TrendRange): number | null {
+function getTrendCutoffMs(db: DatabaseSync, range: TrendRange): string | null {
   if (range === 'all') {
     return null;
   }
-  const dayLimit = getTrendDayLimit(range);
-  const now = new Date();
-  const localMidnight = new Date(now.getFullYear(), now.getMonth(), now.getDate()).getTime();
-  return localMidnight - (dayLimit - 1) * 86_400_000;
+  return getShiftedLocalDayTimestamp(db, currentDbTimestamp(), -(getTrendDayLimit(range) - 1));
+}
+
+function dayPartsFromEpochDay(epochDay: number): { year: number; month: number; day: number } {
+  const z = epochDay + 719468;
+  const era = Math.floor(z / 146097);
+  const doe = z - era * 146097;
+  const yoe = Math.floor(
+    (doe - Math.floor(doe / 1460) + Math.floor(doe / 36524) - Math.floor(doe / 146096)) / 365,
+  );
+  let year = yoe + era * 400;
+  const doy = doe - (365 * yoe + Math.floor(yoe / 4) - Math.floor(yoe / 100));
+  const mp = Math.floor((5 * doy + 2) / 153);
+  const day = doy - Math.floor((153 * mp + 2) / 5) + 1;
+  const month = mp < 10 ? mp + 3 : mp - 9;
+  if (month <= 2) {
+    year += 1;
+  }
+  return { year, month, day };
 }
 
 function makeTrendLabel(value: number): string {
   if (value > 100_000) {
     const year = Math.floor(value / 100);
     const month = value % 100;
-    return new Date(Date.UTC(year, month - 1, 1)).toLocaleDateString(undefined, {
-      month: 'short',
-      year: '2-digit',
-    });
+    return `${MONTH_NAMES[month - 1]} ${String(year).slice(-2)}`;
   }
 
-  return new Date(value * 86_400_000).toLocaleDateString(undefined, {
-    month: 'short',
-    day: 'numeric',
-  });
-}
-
-function getLocalEpochDay(timestampMs: number): number {
-  const date = new Date(timestampMs);
-  return Math.floor((timestampMs - date.getTimezoneOffset() * 60_000) / 86_400_000);
-}
-
-function getLocalDateForEpochDay(epochDay: number): Date {
-  const utcDate = new Date(epochDay * 86_400_000);
-  return new Date(utcDate.getTime() + utcDate.getTimezoneOffset() * 60_000);
-}
-
-function getLocalMonthKey(timestampMs: number): number {
-  const date = new Date(timestampMs);
-  return date.getFullYear() * 100 + date.getMonth() + 1;
+  const { month, day } = dayPartsFromEpochDay(value);
+  return `${MONTH_NAMES[month - 1]} ${day}`;
 }
 
 function getTrendSessionWordCount(session: Pick<TrendSessionMetricRow, 'tokensSeen'>): number {
@@ -189,7 +203,7 @@ function buildAggregatedTrendRows(rollups: ImmersionSessionRollupRow[]) {
 function buildWatchTimeByDayOfWeek(sessions: TrendSessionMetricRow[]): TrendChartPoint[] {
   const totals = new Array(7).fill(0);
   for (const session of sessions) {
-    totals[new Date(session.startedAtMs).getDay()] += session.activeWatchedMs;
+    totals[session.dayOfWeek] += session.activeWatchedMs;
   }
   return DAY_NAMES.map((name, index) => ({
     label: name,
@@ -200,7 +214,7 @@ function buildWatchTimeByDayOfWeek(sessions: TrendSessionMetricRow[]): TrendChar
 function buildWatchTimeByHour(sessions: TrendSessionMetricRow[]): TrendChartPoint[] {
   const totals = new Array(24).fill(0);
   for (const session of sessions) {
-    totals[new Date(session.startedAtMs).getHours()] += session.activeWatchedMs;
+    totals[session.hourOfDay] += session.activeWatchedMs;
   }
   return totals.map((ms, index) => ({
     label: `${String(index).padStart(2, '0')}:00`,
@@ -209,10 +223,8 @@ function buildWatchTimeByHour(sessions: TrendSessionMetricRow[]): TrendChartPoin
 }
 
 function dayLabel(epochDay: number): string {
-  return getLocalDateForEpochDay(epochDay).toLocaleDateString(undefined, {
-    month: 'short',
-    day: 'numeric',
-  });
+  const { month, day } = dayPartsFromEpochDay(epochDay);
+  return `${MONTH_NAMES[month - 1]} ${day}`;
 }
 
 function buildSessionSeriesByDay(
@@ -221,8 +233,7 @@ function buildSessionSeriesByDay(
 ): TrendChartPoint[] {
   const byDay = new Map<number, number>();
   for (const session of sessions) {
-    const epochDay = getLocalEpochDay(session.startedAtMs);
-    byDay.set(epochDay, (byDay.get(epochDay) ?? 0) + getValue(session));
+    byDay.set(session.epochDay, (byDay.get(session.epochDay) ?? 0) + getValue(session));
   }
   return Array.from(byDay.entries())
     .sort(([left], [right]) => left - right)
@@ -235,8 +246,7 @@ function buildSessionSeriesByMonth(
 ): TrendChartPoint[] {
   const byMonth = new Map<number, number>();
   for (const session of sessions) {
-    const monthKey = getLocalMonthKey(session.startedAtMs);
-    byMonth.set(monthKey, (byMonth.get(monthKey) ?? 0) + getValue(session));
+    byMonth.set(session.monthKey, (byMonth.get(session.monthKey) ?? 0) + getValue(session));
   }
   return Array.from(byMonth.entries())
     .sort(([left], [right]) => left - right)
@@ -251,8 +261,7 @@ function buildLookupsPerHundredWords(
   const wordsByBucket = new Map<number, number>();
 
   for (const session of sessions) {
-    const bucketKey =
-      groupBy === 'month' ? getLocalMonthKey(session.startedAtMs) : getLocalEpochDay(session.startedAtMs);
+    const bucketKey = groupBy === 'month' ? session.monthKey : session.epochDay;
     lookupsByBucket.set(
       bucketKey,
       (lookupsByBucket.get(bucketKey) ?? 0) + session.yomitanLookupCount,
@@ -282,7 +291,7 @@ function buildPerAnimeFromSessions(
 
   for (const session of sessions) {
     const animeTitle = resolveTrendAnimeTitle(session);
-    const epochDay = getLocalEpochDay(session.startedAtMs);
+    const epochDay = session.epochDay;
     const dayMap = byAnime.get(animeTitle) ?? new Map();
     dayMap.set(epochDay, (dayMap.get(epochDay) ?? 0) + getValue(session));
     byAnime.set(animeTitle, dayMap);
@@ -303,7 +312,7 @@ function buildLookupsPerHundredPerAnime(sessions: TrendSessionMetricRow[]): Tren
 
   for (const session of sessions) {
     const animeTitle = resolveTrendAnimeTitle(session);
-    const epochDay = getLocalEpochDay(session.startedAtMs);
+    const epochDay = session.epochDay;
 
     const lookupMap = lookups.get(animeTitle) ?? new Map();
     lookupMap.set(epochDay, (lookupMap.get(epochDay) ?? 0) + session.yomitanLookupCount);
@@ -498,9 +507,10 @@ function buildEpisodesPerMonthFromRollups(rollups: ImmersionSessionRollupRow[]):
 
 function getTrendSessionMetrics(
   db: DatabaseSync,
-  cutoffMs: number | null,
+  cutoffMs: string | null,
 ): TrendSessionMetricRow[] {
   const whereClause = cutoffMs === null ? '' : 'WHERE s.started_at_ms >= ?';
+  const cutoffValue = cutoffMs === null ? null : toDbTimestamp(cutoffMs);
   const prepared = db.prepare(`
     ${ACTIVE_SESSION_METRICS_CTE}
     SELECT
@@ -520,14 +530,27 @@ function getTrendSessionMetrics(
     ORDER BY s.started_at_ms ASC
   `);
 
-  return (cutoffMs === null ? prepared.all() : prepared.all(cutoffMs)) as TrendSessionMetricRow[];
+  const rows = (cutoffValue === null ? prepared.all() : prepared.all(cutoffValue)) as Array<
+    TrendSessionMetricRow & { startedAtMs: number | string }
+  >;
+  return rows.map((row) => ({
+    ...row,
+    startedAtMs: 0,
+    epochDay: getLocalEpochDay(db, row.startedAtMs),
+    monthKey: getLocalMonthKey(db, row.startedAtMs),
+    dayOfWeek: getLocalDayOfWeek(db, row.startedAtMs),
+    hourOfDay: getLocalHourOfDay(db, row.startedAtMs),
+  }));
 }
 
-function buildNewWordsPerDay(db: DatabaseSync, cutoffMs: number | null): TrendChartPoint[] {
+function buildNewWordsPerDay(db: DatabaseSync, cutoffMs: string | null): TrendChartPoint[] {
   const whereClause = cutoffMs === null ? '' : 'AND first_seen >= ?';
   const prepared = db.prepare(`
     SELECT
-      CAST(julianday(first_seen, 'unixepoch', 'localtime') - 2440587.5 AS INTEGER) AS epochDay,
+      CAST(
+        julianday(CAST(first_seen AS REAL), 'unixepoch', 'localtime') - 2440587.5
+        AS INTEGER
+      ) AS epochDay,
       COUNT(*) AS wordCount
     FROM imm_words
     WHERE first_seen IS NOT NULL
@@ -537,7 +560,7 @@ function buildNewWordsPerDay(db: DatabaseSync, cutoffMs: number | null): TrendCh
   `);
 
   const rows = (
-    cutoffMs === null ? prepared.all() : prepared.all(Math.floor(cutoffMs / 1000))
+    cutoffMs === null ? prepared.all() : prepared.all((BigInt(cutoffMs) / 1000n).toString())
   ) as Array<{
     epochDay: number;
     wordCount: number;
@@ -549,11 +572,14 @@ function buildNewWordsPerDay(db: DatabaseSync, cutoffMs: number | null): TrendCh
   }));
 }
 
-function buildNewWordsPerMonth(db: DatabaseSync, cutoffMs: number | null): TrendChartPoint[] {
+function buildNewWordsPerMonth(db: DatabaseSync, cutoffMs: string | null): TrendChartPoint[] {
   const whereClause = cutoffMs === null ? '' : 'AND first_seen >= ?';
   const prepared = db.prepare(`
     SELECT
-      CAST(strftime('%Y%m', first_seen, 'unixepoch', 'localtime') AS INTEGER) AS monthKey,
+      CAST(
+        strftime('%Y%m', CAST(first_seen AS REAL), 'unixepoch', 'localtime')
+        AS INTEGER
+      ) AS monthKey,
       COUNT(*) AS wordCount
     FROM imm_words
     WHERE first_seen IS NOT NULL
@@ -563,7 +589,7 @@ function buildNewWordsPerMonth(db: DatabaseSync, cutoffMs: number | null): Trend
   `);
 
   const rows = (
-    cutoffMs === null ? prepared.all() : prepared.all(Math.floor(cutoffMs / 1000))
+    cutoffMs === null ? prepared.all() : prepared.all((BigInt(cutoffMs) / 1000n).toString())
   ) as Array<{
     monthKey: number;
     wordCount: number;
@@ -581,8 +607,8 @@ export function getTrendsDashboard(
   groupBy: TrendGroupBy = 'day',
 ): TrendsDashboardQueryResult {
   const dayLimit = getTrendDayLimit(range);
-  const monthlyLimit = getTrendMonthlyLimit(range);
-  const cutoffMs = getTrendCutoffMs(range);
+  const monthlyLimit = getTrendMonthlyLimit(db, range);
+  const cutoffMs = getTrendCutoffMs(db, range);
   const useMonthlyBuckets = groupBy === 'month';
   const dailyRollups = getDailyRollups(db, dayLimit);
   const monthlyRollups = getMonthlyRollups(db, monthlyLimit);
diff --git a/src/core/services/immersion-tracker/session.ts b/src/core/services/immersion-tracker/session.ts
index b0484f65..787c246d 100644
--- a/src/core/services/immersion-tracker/session.ts
+++ b/src/core/services/immersion-tracker/session.ts
@@ -4,7 +4,7 @@ import { createInitialSessionState } from './reducer';
 import { nowMs } from './time';
 import { SESSION_STATUS_ACTIVE, SESSION_STATUS_ENDED } from './types';
 import type { SessionState } from './types';
-import { toDbMs } from './query-shared';
+import { toDbMs, toDbTimestamp } from './query-shared';
 
 export function startSessionRecord(
   db: DatabaseSync,
@@ -25,10 +25,10 @@ export function startSessionRecord(
     .run(
       sessionUuid,
       videoId,
-      toDbMs(startedAtMs),
+      toDbTimestamp(startedAtMs),
       SESSION_STATUS_ACTIVE,
-      toDbMs(startedAtMs),
-      toDbMs(createdAtMs),
+      toDbTimestamp(startedAtMs),
+      toDbTimestamp(createdAtMs),
     );
   const sessionId = Number(result.lastInsertRowid);
   return {
@@ -40,7 +40,7 @@ export function startSessionRecord(
 export function finalizeSessionRecord(
   db: DatabaseSync,
   sessionState: SessionState,
-  endedAtMs = nowMs(),
+  endedAtMs: number | string = nowMs(),
 ): void {
   db.prepare(
     `
@@ -66,7 +66,7 @@ export function finalizeSessionRecord(
       WHERE session_id = ?
     `,
   ).run(
-    toDbMs(endedAtMs),
+    toDbTimestamp(endedAtMs),
     SESSION_STATUS_ENDED,
     sessionState.lastMediaMs === null ? null : toDbMs(sessionState.lastMediaMs),
     sessionState.totalWatchedMs,
@@ -82,7 +82,7 @@ export function finalizeSessionRecord(
     sessionState.seekForwardCount,
     sessionState.seekBackwardCount,
     sessionState.mediaBufferEvents,
-    toDbMs(nowMs()),
+    toDbTimestamp(nowMs()),
     sessionState.sessionId,
   );
 }
diff --git a/src/core/services/immersion-tracker/storage-session.test.ts b/src/core/services/immersion-tracker/storage-session.test.ts
index d00e09bd..d84a8496 100644
--- a/src/core/services/immersion-tracker/storage-session.test.ts
+++ b/src/core/services/immersion-tracker/storage-session.test.ts
@@ -143,10 +143,10 @@ test('ensureSchema creates immersion core tables', () => {
     const rollupStateRow = db
       .prepare('SELECT state_value FROM imm_rollup_state WHERE state_key = ?')
       .get('last_rollup_sample_ms') as {
-      state_value: number;
+      state_value: string;
     } | null;
     assert.ok(rollupStateRow);
-    assert.equal(rollupStateRow?.state_value, 0);
+    assert.equal(Number(rollupStateRow?.state_value ?? 0), 0);
   } finally {
     db.close();
     cleanupDbPath(dbPath);
@@ -965,12 +965,12 @@ test('start/finalize session updates ended_at and status', () => {
     const row = db
       .prepare('SELECT ended_at_ms, status FROM imm_sessions WHERE session_id = ?')
       .get(sessionId) as {
-      ended_at_ms: number | null;
+      ended_at_ms: string | null;
       status: number;
     } | null;
 
     assert.ok(row);
-    assert.equal(row?.ended_at_ms, endedAtMs);
+    assert.equal(Number(row?.ended_at_ms ?? 0), endedAtMs);
     assert.equal(row?.status, SESSION_STATUS_ENDED);
   } finally {
     db.close();
diff --git a/src/core/services/immersion-tracker/storage.ts b/src/core/services/immersion-tracker/storage.ts
index ce8833cc..98496868 100644
--- a/src/core/services/immersion-tracker/storage.ts
+++ b/src/core/services/immersion-tracker/storage.ts
@@ -4,7 +4,7 @@ import type { DatabaseSync } from './sqlite';
 import { nowMs } from './time';
 import { SCHEMA_VERSION } from './types';
 import type { QueuedWrite, VideoMetadata, YoutubeVideoMetadata } from './types';
-import { toDbMs } from './query-shared';
+import { toDbMs, toDbTimestamp } from './query-shared';
 
 export interface TrackerPreparedStatements {
   telemetryInsertStmt: ReturnType<DatabaseSync['prepare']>;
@@ -130,7 +130,7 @@ function deduplicateExistingCoverArtRows(db: DatabaseSync): void {
     return;
   }
 
-  const nowMsValue = toDbMs(nowMs());
+  const nowMsValue = toDbTimestamp(nowMs());
   const upsertBlobStmt = db.prepare(`
     INSERT INTO imm_cover_art_blobs (blob_hash, cover_blob, CREATED_DATE, LAST_UPDATE_DATE)
     VALUES (?, ?, ?, ?)
@@ -275,7 +275,7 @@ function parseLegacyAnimeBackfillCandidate(
 }
 
 function ensureLifetimeSummaryTables(db: DatabaseSync): void {
-  const nowMsValue = toDbMs(nowMs());
+  const nowMsValue = toDbTimestamp(nowMs());
 
   db.exec(`
     CREATE TABLE IF NOT EXISTS imm_lifetime_global(
@@ -287,9 +287,9 @@ function ensureLifetimeSummaryTables(db: DatabaseSync): void {
       episodes_started INTEGER NOT NULL DEFAULT 0,
       episodes_completed INTEGER NOT NULL DEFAULT 0,
       anime_completed INTEGER NOT NULL DEFAULT 0,
-      last_rebuilt_ms INTEGER,
-      CREATED_DATE INTEGER,
-      LAST_UPDATE_DATE INTEGER
+      last_rebuilt_ms TEXT,
+      CREATED_DATE TEXT,
+      LAST_UPDATE_DATE TEXT
     )
   `);
 
@@ -332,10 +332,10 @@ function ensureLifetimeSummaryTables(db: DatabaseSync): void {
       total_tokens_seen INTEGER NOT NULL DEFAULT 0,
       episodes_started INTEGER NOT NULL DEFAULT 0,
       episodes_completed INTEGER NOT NULL DEFAULT 0,
-      first_watched_ms INTEGER,
-      last_watched_ms INTEGER,
-      CREATED_DATE INTEGER,
-      LAST_UPDATE_DATE INTEGER,
+      first_watched_ms TEXT,
+      last_watched_ms TEXT,
+      CREATED_DATE TEXT,
+      LAST_UPDATE_DATE TEXT,
       FOREIGN KEY(anime_id) REFERENCES imm_anime(anime_id) ON DELETE CASCADE
     )
   `);
@@ -349,10 +349,10 @@ function ensureLifetimeSummaryTables(db: DatabaseSync): void {
       total_lines_seen INTEGER NOT NULL DEFAULT 0,
       total_tokens_seen INTEGER NOT NULL DEFAULT 0,
       completed INTEGER NOT NULL DEFAULT 0,
-      first_watched_ms INTEGER,
-      last_watched_ms INTEGER,
-      CREATED_DATE INTEGER,
-      LAST_UPDATE_DATE INTEGER,
+      first_watched_ms TEXT,
+      last_watched_ms TEXT,
+      CREATED_DATE TEXT,
+      LAST_UPDATE_DATE TEXT,
       FOREIGN KEY(video_id) REFERENCES imm_videos(video_id) ON DELETE CASCADE
     )
   `);
@@ -360,9 +360,9 @@ function ensureLifetimeSummaryTables(db: DatabaseSync): void {
   db.exec(`
     CREATE TABLE IF NOT EXISTS imm_lifetime_applied_sessions(
       session_id INTEGER PRIMARY KEY,
-      applied_at_ms INTEGER NOT NULL,
-      CREATED_DATE INTEGER,
-      LAST_UPDATE_DATE INTEGER,
+      applied_at_ms TEXT NOT NULL,
+      CREATED_DATE TEXT,
+      LAST_UPDATE_DATE TEXT,
       FOREIGN KEY(session_id) REFERENCES imm_sessions(session_id) ON DELETE CASCADE
     )
   `);
@@ -405,13 +405,13 @@ export function getOrCreateAnimeRecord(db: DatabaseSync, input: AnimeRecordInput
       input.titleEnglish,
       input.titleNative,
       input.metadataJson,
-      toDbMs(nowMs()),
+      toDbTimestamp(nowMs()),
       existing.anime_id,
     );
     return existing.anime_id;
   }
 
-  const nowMsValue = toDbMs(nowMs());
+  const nowMsValue = toDbTimestamp(nowMs());
   const result = db
     .prepare(
       `
@@ -471,7 +471,7 @@ export function linkVideoToAnimeRecord(
     input.parserSource,
     input.parserConfidence,
     input.parseMetadataJson,
-    toDbMs(nowMs()),
+    toDbTimestamp(nowMs()),
     videoId,
   );
 }
@@ -562,13 +562,13 @@ export function ensureSchema(db: DatabaseSync): void {
   db.exec(`
     CREATE TABLE IF NOT EXISTS imm_schema_version (
       schema_version INTEGER PRIMARY KEY,
-      applied_at_ms INTEGER NOT NULL
+      applied_at_ms TEXT NOT NULL
     );
   `);
   db.exec(`
     CREATE TABLE IF NOT EXISTS imm_rollup_state(
       state_key TEXT PRIMARY KEY,
-      state_value INTEGER NOT NULL
+      state_value TEXT NOT NULL
     );
   `);
   db.exec(`
@@ -597,8 +597,8 @@ export function ensureSchema(db: DatabaseSync): void {
       episodes_total INTEGER,
       description TEXT,
       metadata_json TEXT,
-      CREATED_DATE INTEGER,
-      LAST_UPDATE_DATE INTEGER
+      CREATED_DATE TEXT,
+      LAST_UPDATE_DATE TEXT
     );
   `);
   db.exec(`
@@ -625,8 +625,8 @@ export function ensureSchema(db: DatabaseSync): void {
       bitrate_kbps INTEGER, audio_codec_id INTEGER,
       hash_sha256 TEXT, screenshot_path TEXT,
       metadata_json TEXT,
-      CREATED_DATE INTEGER,
-      LAST_UPDATE_DATE INTEGER,
+      CREATED_DATE TEXT,
+      LAST_UPDATE_DATE TEXT,
       FOREIGN KEY(anime_id) REFERENCES imm_anime(anime_id) ON DELETE SET NULL
     );
   `);
@@ -635,7 +635,7 @@ export function ensureSchema(db: DatabaseSync): void {
       session_id INTEGER PRIMARY KEY AUTOINCREMENT,
       session_uuid TEXT NOT NULL UNIQUE,
       video_id INTEGER NOT NULL,
-      started_at_ms INTEGER NOT NULL, ended_at_ms INTEGER,
+      started_at_ms TEXT NOT NULL, ended_at_ms TEXT,
       status INTEGER NOT NULL,
       locale_id INTEGER, target_lang_id INTEGER,
       difficulty_tier INTEGER, subtitle_mode INTEGER,
@@ -653,8 +653,8 @@ export function ensureSchema(db: DatabaseSync): void {
       seek_forward_count INTEGER NOT NULL DEFAULT 0,
       seek_backward_count INTEGER NOT NULL DEFAULT 0,
       media_buffer_events INTEGER NOT NULL DEFAULT 0,
-      CREATED_DATE INTEGER,
-      LAST_UPDATE_DATE INTEGER,
+      CREATED_DATE TEXT,
+      LAST_UPDATE_DATE TEXT,
       FOREIGN KEY(video_id) REFERENCES imm_videos(video_id)
     );
   `);
@@ -662,7 +662,7 @@ export function ensureSchema(db: DatabaseSync): void {
     CREATE TABLE IF NOT EXISTS imm_session_telemetry(
       telemetry_id INTEGER PRIMARY KEY AUTOINCREMENT,
       session_id INTEGER NOT NULL,
-      sample_ms INTEGER NOT NULL,
+      sample_ms TEXT NOT NULL,
       total_watched_ms INTEGER NOT NULL DEFAULT 0,
       active_watched_ms INTEGER NOT NULL DEFAULT 0,
       lines_seen INTEGER NOT NULL DEFAULT 0,
@@ -676,8 +676,8 @@ export function ensureSchema(db: DatabaseSync): void {
       seek_forward_count INTEGER NOT NULL DEFAULT 0,
       seek_backward_count INTEGER NOT NULL DEFAULT 0,
       media_buffer_events INTEGER NOT NULL DEFAULT 0,
-      CREATED_DATE INTEGER,
-      LAST_UPDATE_DATE INTEGER,
+      CREATED_DATE TEXT,
+      LAST_UPDATE_DATE TEXT,
       FOREIGN KEY(session_id) REFERENCES imm_sessions(session_id) ON DELETE CASCADE
     );
   `);
@@ -693,8 +693,8 @@ export function ensureSchema(db: DatabaseSync): void {
       tokens_delta INTEGER NOT NULL DEFAULT 0,
       cards_delta INTEGER NOT NULL DEFAULT 0,
       payload_json TEXT,
-      CREATED_DATE INTEGER,
-      LAST_UPDATE_DATE INTEGER,
+      CREATED_DATE TEXT,
+      LAST_UPDATE_DATE TEXT,
       FOREIGN KEY(session_id) REFERENCES imm_sessions(session_id) ON DELETE CASCADE
     );
   `);
@@ -710,8 +710,8 @@ export function ensureSchema(db: DatabaseSync): void {
       cards_per_hour REAL,
       tokens_per_min REAL,
       lookup_hit_rate REAL,
-      CREATED_DATE INTEGER,
-      LAST_UPDATE_DATE INTEGER,
+      CREATED_DATE TEXT,
+      LAST_UPDATE_DATE TEXT,
       PRIMARY KEY (rollup_day, video_id)
     );
   `);
@@ -724,8 +724,8 @@ export function ensureSchema(db: DatabaseSync): void {
       total_lines_seen INTEGER NOT NULL DEFAULT 0,
       total_tokens_seen INTEGER NOT NULL DEFAULT 0,
       total_cards INTEGER NOT NULL DEFAULT 0,
-      CREATED_DATE INTEGER,
-      LAST_UPDATE_DATE INTEGER,
+      CREATED_DATE TEXT,
+      LAST_UPDATE_DATE TEXT,
       PRIMARY KEY (rollup_month, video_id)
     );
   `);
@@ -806,9 +806,9 @@ export function ensureSchema(db: DatabaseSync): void {
       title_romaji TEXT,
       title_english TEXT,
       episodes_total INTEGER,
-      fetched_at_ms INTEGER NOT NULL,
-      CREATED_DATE INTEGER,
-      LAST_UPDATE_DATE INTEGER,
+      fetched_at_ms TEXT NOT NULL,
+      CREATED_DATE TEXT,
+      LAST_UPDATE_DATE TEXT,
       FOREIGN KEY(video_id) REFERENCES imm_videos(video_id) ON DELETE CASCADE
     );
   `);
@@ -827,9 +827,9 @@ export function ensureSchema(db: DatabaseSync): void {
       uploader_url TEXT,
       description TEXT,
       metadata_json TEXT,
-      fetched_at_ms INTEGER NOT NULL,
-      CREATED_DATE INTEGER,
-      LAST_UPDATE_DATE INTEGER,
+      fetched_at_ms TEXT NOT NULL,
+      CREATED_DATE TEXT,
+      LAST_UPDATE_DATE TEXT,
       FOREIGN KEY(video_id) REFERENCES imm_videos(video_id) ON DELETE CASCADE
     );
   `);
@@ -837,26 +837,26 @@ export function ensureSchema(db: DatabaseSync): void {
     CREATE TABLE IF NOT EXISTS imm_cover_art_blobs(
       blob_hash TEXT PRIMARY KEY,
       cover_blob BLOB NOT NULL,
-      CREATED_DATE INTEGER,
-      LAST_UPDATE_DATE INTEGER
+      CREATED_DATE TEXT,
+      LAST_UPDATE_DATE TEXT
     );
   `);
 
   if (currentVersion?.schema_version === 1) {
-    addColumnIfMissing(db, 'imm_videos', 'CREATED_DATE');
-    addColumnIfMissing(db, 'imm_videos', 'LAST_UPDATE_DATE');
-    addColumnIfMissing(db, 'imm_sessions', 'CREATED_DATE');
-    addColumnIfMissing(db, 'imm_sessions', 'LAST_UPDATE_DATE');
-    addColumnIfMissing(db, 'imm_session_telemetry', 'CREATED_DATE');
-    addColumnIfMissing(db, 'imm_session_telemetry', 'LAST_UPDATE_DATE');
-    addColumnIfMissing(db, 'imm_session_events', 'CREATED_DATE');
-    addColumnIfMissing(db, 'imm_session_events', 'LAST_UPDATE_DATE');
-    addColumnIfMissing(db, 'imm_daily_rollups', 'CREATED_DATE');
-    addColumnIfMissing(db, 'imm_daily_rollups', 'LAST_UPDATE_DATE');
-    addColumnIfMissing(db, 'imm_monthly_rollups', 'CREATED_DATE');
-    addColumnIfMissing(db, 'imm_monthly_rollups', 'LAST_UPDATE_DATE');
+    addColumnIfMissing(db, 'imm_videos', 'CREATED_DATE', 'TEXT');
+    addColumnIfMissing(db, 'imm_videos', 'LAST_UPDATE_DATE', 'TEXT');
+    addColumnIfMissing(db, 'imm_sessions', 'CREATED_DATE', 'TEXT');
+    addColumnIfMissing(db, 'imm_sessions', 'LAST_UPDATE_DATE', 'TEXT');
+    addColumnIfMissing(db, 'imm_session_telemetry', 'CREATED_DATE', 'TEXT');
+    addColumnIfMissing(db, 'imm_session_telemetry', 'LAST_UPDATE_DATE', 'TEXT');
+    addColumnIfMissing(db, 'imm_session_events', 'CREATED_DATE', 'TEXT');
+    addColumnIfMissing(db, 'imm_session_events', 'LAST_UPDATE_DATE', 'TEXT');
+    addColumnIfMissing(db, 'imm_daily_rollups', 'CREATED_DATE', 'TEXT');
+    addColumnIfMissing(db, 'imm_daily_rollups', 'LAST_UPDATE_DATE', 'TEXT');
+    addColumnIfMissing(db, 'imm_monthly_rollups', 'CREATED_DATE', 'TEXT');
+    addColumnIfMissing(db, 'imm_monthly_rollups', 'LAST_UPDATE_DATE', 'TEXT');
 
-    const migratedAtMs = toDbMs(nowMs());
+    const migratedAtMs = toDbTimestamp(nowMs());
     db.prepare(
       `
         UPDATE imm_videos
@@ -1243,7 +1243,7 @@ export function ensureSchema(db: DatabaseSync): void {
 
   db.exec(`
     INSERT INTO imm_schema_version(schema_version, applied_at_ms)
-    VALUES (${SCHEMA_VERSION}, ${toDbMs(nowMs())})
+    VALUES (${SCHEMA_VERSION}, ${toDbTimestamp(nowMs())})
     ON CONFLICT DO NOTHING
   `);
 }
@@ -1401,7 +1401,7 @@ function incrementKanjiAggregate(
 }
 
 export function executeQueuedWrite(write: QueuedWrite, stmts: TrackerPreparedStatements): void {
-  const currentMs = toDbMs(nowMs());
+  const currentMs = toDbTimestamp(nowMs());
   if (write.kind === 'telemetry') {
     if (
       write.totalWatchedMs === undefined ||
@@ -1420,7 +1420,7 @@ export function executeQueuedWrite(write: QueuedWrite, stmts: TrackerPreparedSta
     ) {
       throw new Error('Incomplete telemetry write');
     }
-    const telemetrySampleMs = toDbMs(write.sampleMs ?? Number(currentMs));
+    const telemetrySampleMs = toDbTimestamp(write.sampleMs ?? Number(currentMs));
     stmts.telemetryInsertStmt.run(
       write.sessionId,
       telemetrySampleMs,
@@ -1495,7 +1495,7 @@ export function executeQueuedWrite(write: QueuedWrite, stmts: TrackerPreparedSta
 
   stmts.eventInsertStmt.run(
     write.sessionId,
-    toDbMs(write.sampleMs ?? Number(currentMs)),
+    toDbTimestamp(write.sampleMs ?? Number(currentMs)),
     write.eventType ?? 0,
     write.lineIndex ?? null,
     write.segmentStartMs ?? null,
@@ -1530,11 +1530,11 @@ export function getOrCreateVideoRecord(
           LAST_UPDATE_DATE = ?
         WHERE video_id = ?
       `,
-    ).run(details.canonicalTitle || 'unknown', toDbMs(nowMs()), existing.video_id);
+    ).run(details.canonicalTitle || 'unknown', toDbTimestamp(nowMs()), existing.video_id);
     return existing.video_id;
   }
 
-  const currentMs = toDbMs(nowMs());
+  const currentMs = toDbTimestamp(nowMs());
   const insert = db.prepare(`
     INSERT INTO imm_videos (
       video_key, canonical_title, source_type, source_path, source_url,
@@ -1604,7 +1604,7 @@ export function updateVideoMetadataRecord(
     metadata.hashSha256,
     metadata.screenshotPath,
     metadata.metadataJson,
-    toDbMs(nowMs()),
+    toDbTimestamp(nowMs()),
     videoId,
   );
 }
@@ -1622,7 +1622,7 @@ export function updateVideoTitleRecord(
         LAST_UPDATE_DATE = ?
       WHERE video_id = ?
     `,
-  ).run(canonicalTitle, toDbMs(nowMs()), videoId);
+  ).run(canonicalTitle, toDbTimestamp(nowMs()), videoId);
 }
 
 export function upsertYoutubeVideoMetadata(
@@ -1630,7 +1630,7 @@ export function upsertYoutubeVideoMetadata(
   videoId: number,
   metadata: YoutubeVideoMetadata,
 ): void {
-  const currentMs = toDbMs(nowMs());
+  const currentMs = toDbTimestamp(nowMs());
   db.prepare(
     `
       INSERT INTO imm_youtube_videos (
diff --git a/src/core/services/immersion-tracker/time.ts b/src/core/services/immersion-tracker/time.ts
index 8ea20816..11205c83 100644
--- a/src/core/services/immersion-tracker/time.ts
+++ b/src/core/services/immersion-tracker/time.ts
@@ -1,4 +1,13 @@
+declare global {
+  var __subminerTestNowMs: number | string | undefined;
+}
+
 export function nowMs(): number {
+  const testNowMs = globalThis.__subminerTestNowMs;
+  if (typeof testNowMs === 'number' && Number.isFinite(testNowMs)) {
+    return Math.floor(testNowMs);
+  }
+
   const perf = globalThis.performance;
   if (perf && Number.isFinite(perf.timeOrigin)) {
     return Math.floor(perf.timeOrigin + perf.now());