diff --git a/apps/docs/cost-analytics.mdx b/apps/docs/cost-analytics.mdx
index 0a2a3dc27d..b0b1b874a4 100644
--- a/apps/docs/cost-analytics.mdx
+++ b/apps/docs/cost-analytics.mdx
@@ -34,6 +34,11 @@ model and provider. The source also appears in the detail drilldown. Choose a
 time range before comparing periods so the chart and breakdown use the same
 window.
 
+Analytics date presets and daily chart buckets use the web server's timezone,
+including daylight-saving transitions. Costs, Tasks, and PR analytics use the
+same calendar-day boundaries; these are not based on each viewer's browser
+timezone or the deployment's automation scheduling timezone.
+
 ## Exporting data
 
 Select **Download data** to export the currently filtered detail rows as a CSV
diff --git a/apps/web/src/lib/server/analytics/time-buckets.ts b/apps/web/src/lib/server/analytics/time-buckets.ts
index 88c6e70076..92d353e561 100644
--- a/apps/web/src/lib/server/analytics/time-buckets.ts
+++ b/apps/web/src/lib/server/analytics/time-buckets.ts
@@ -35,14 +35,7 @@ export function getRequestTimeBootstrapCutoff(
   timePeriod: TimePeriodFilter | undefined,
   now: Date,
 ): Date | null {
-  if (!timePeriod || timePeriod === 'all') {
-    return null;
-  }
-
-  const cutoff = new Date(now);
-  cutoff.setUTCHours(0, 0, 0, 0);
-  cutoff.setUTCDate(cutoff.getUTCDate() - (timePeriod - 1));
-  return cutoff;
+  return getTimeCutoff(timePeriod, now);
 }
 
 export function getResolvedGranularity(
diff --git a/apps/web/src/lib/server/pull-request-facts.test.ts b/apps/web/src/lib/server/pull-request-facts.test.ts
new file mode 100644
index 0000000000..4a07c37350
--- /dev/null
+++ b/apps/web/src/lib/server/pull-request-facts.test.ts
@@ -0,0 +1,96 @@
+import {
+  db,
+  eq,
+  pullRequestFacts,
+  repositories,
+  repositoryFactory,
+  userFactory,
+  users,
+} from '@roomote/db/server';
+
+import { getRequestTimeBootstrapCutoff } from './analytics/time-buckets';
+import { getStoredPullRequestsForAnalytics } from './pull-request-facts';
+
+const cases = [
+  ['America/Los_Angeles', '2026-09-07T02:00:00Z', '2026-09-06T07:00:00Z'],
+  ['Asia/Tokyo', '2026-09-07T02:00:00Z', '2026-09-06T15:00:00Z'],
+  ['America/Los_Angeles', '2026-03-08T12:00:00Z', '2026-03-08T08:00:00Z'],
+  ['America/Los_Angeles', '2025-11-02T12:00:00Z', '2025-11-02T07:00:00Z'],
+];
+
+describe('PR analytics calendar-day cutoffs', () => {
+  let repositoryId: string;
+  let userId: string;
+
+  beforeAll(async () => {
+    const user = await userFactory.create();
+    userId = user.id;
+    const repository = await repositoryFactory.create({
+      sourceControlProvider: 'gitea',
+      linkedByUserId: userId,
+    });
+    repositoryId = repository.id;
+  });
+
+  afterEach(async () => {
+    vi.unstubAllEnvs();
+    await db
+      .delete(pullRequestFacts)
+      .where(eq(pullRequestFacts.repositoryId, repositoryId));
+  });
+
+  afterAll(async () => {
+    await db.delete(repositories).where(eq(repositories.id, repositoryId));
+    await db.delete(users).where(eq(users.id, userId));
+  });
+
+  it.each(cases)(
+    'filters stored PRs at local midnight in %s at %s',
+    async (tz, timestamp, cutoff) => {
+      vi.stubEnv('TZ', tz!);
+      const start = new Date(cutoff!);
+      await db.insert(pullRequestFacts).values(
+        [-1, 0, 3600000].map((offset, index) => ({
+          repositoryId,
+          repositoryFullName: 'fixture/calendar-days',
+          sourceControlProvider: 'gitea' as const,
+          externalPullRequestId: index + 1,
+          prNumber: index + 1,
+          title: `Boundary ${index}`,
+          htmlUrl: `https://example.invalid/pulls/${index + 1}`,
+          state: 'open' as const,
+          createdAtRemote: new Date(start.getTime() + offset),
+          updatedAtRemote: new Date(start.getTime() + offset),
+        })),
+      );
+
+      const rows = await getStoredPullRequestsForAnalytics({
+        repositoryIds: [repositoryId],
+        timePeriod: 1,
+        now: new Date(timestamp!),
+      });
+      expect(rows.map((row) => row.number).sort()).toEqual([2, 3]);
+      const allRows = await getStoredPullRequestsForAnalytics({
+        repositoryIds: [repositoryId],
+        timePeriod: 'all',
+        now: new Date(timestamp!),
+      });
+      expect(allRows).toHaveLength(3);
+    },
+  );
+
+  it.each(cases)(
+    'bootstraps the same local day in %s at %s',
+    (tz, timestamp, cutoff) => {
+      vi.stubEnv('TZ', tz!);
+      expect(getRequestTimeBootstrapCutoff(1, new Date(timestamp!))).toEqual(
+        new Date(cutoff!),
+      );
+    },
+  );
+
+  it('does not bound an all-time or unspecified bootstrap', () => {
+    expect(getRequestTimeBootstrapCutoff('all', new Date())).toBeNull();
+    expect(getRequestTimeBootstrapCutoff(undefined, new Date())).toBeNull();
+  });
+});
diff --git a/apps/web/src/lib/server/pull-request-facts.ts b/apps/web/src/lib/server/pull-request-facts.ts
index 465b63c9c0..8f9ef50e06 100644
--- a/apps/web/src/lib/server/pull-request-facts.ts
+++ b/apps/web/src/lib/server/pull-request-facts.ts
@@ -10,20 +10,7 @@ import {
 } from '@roomote/db/server';
 
 import type { TimePeriodFilter } from '@/types';
-
-function getTimeCutoff(
-  timePeriod: TimePeriodFilter | undefined,
-  now: Date,
-): Date | null {
-  if (!timePeriod || timePeriod === 'all') {
-    return null;
-  }
-
-  const cutoff = new Date(now);
-  cutoff.setUTCHours(0, 0, 0, 0);
-  cutoff.setUTCDate(cutoff.getUTCDate() - (timePeriod - 1));
-  return cutoff;
-}
+import { getTimeCutoff } from './analytics/time-buckets';
 
 export async function getStoredPullRequestsForAnalytics(params: {
   repositoryIds: string[];