diff --git a/docs/api/openapi.yaml b/docs/api/openapi.yaml
index 20072acf6..80bd0007c 100644
--- a/docs/api/openapi.yaml
+++ b/docs/api/openapi.yaml
@@ -70819,9 +70819,10 @@ components:
               format: date-time
               pattern: ^(?:(?:\d\d[2468][048]|\d\d[13579][26]|\d\d0[48]|[02468][048]00|[13579][26]00)-02-29|\d{4}-(?:(?:0[13578]|1[02])-(?:0[1-9]|[12]\d|3[01])|(?:0[469]|11)-(?:0[1-9]|[12]\d|30)|(?:02)-(?:0[1-9]|1\d|2[0-8])))T(?:(?:[01]\d|2[0-3]):[0-5]\d(?::[0-5]\d(?:\.\d+)?)?(?:Z|([+-](?:[01]\d|2[0-3]):[0-5]\d)))$
             - type: "null"
-          description: Instant behind `latestValue`, falling back to the metric's newest reading. For `mood` this is the day START
-            of the latest daily bucket, not a reading time — the series pins a day, so inventing an instant would be a
-            lie. For `bmi` it is the WEIGHT metadata, since BMI moves exactly when weight does.
+          description: Instant behind `latestValue`, falling back to the metric's newest reading. For `mood` this is the first
+            instant of the latest daily bucket's day in the account's time zone, not a reading time (the series pins a
+            local day, not an instant); formatted in that zone it always lands on the day the entry was logged. For
+            `bmi` it is the WEIGHT metadata, since BMI moves exactly when weight does.
         allTimeCount:
           type: integer
           minimum: -9007199254740991
diff --git a/src/app/api/dashboard/summary/__tests__/route.test.ts b/src/app/api/dashboard/summary/__tests__/route.test.ts
index 57fb570ad..e61286e5b 100644
--- a/src/app/api/dashboard/summary/__tests__/route.test.ts
+++ b/src/app/api/dashboard/summary/__tests__/route.test.ts
@@ -105,6 +105,7 @@ import { prisma } from "@/lib/db";
 import { getSession } from "@/lib/auth/session";
 import { __resetAllCachesForTests } from "@/lib/cache/server-cache";
 import { buildMoodDailySeries } from "@/lib/analytics/mood-series";
+import { userDayKey } from "@/lib/tz/format";
 
 const SESSION_OK = {
   session: { id: "sess-1", expiresAt: new Date(Date.now() + 3_600_000) },
@@ -1167,7 +1168,32 @@ describe("GET /api/dashboard/summary — mood + BMI cards", () => {
     expect(mood?.allTimeCount).toBe(3);
     expect(mood?.titleKey).toBe("dashboard.metric.title.mood");
     expect(mood?.unitKey).toBe("dashboard.metric.unit.mood");
-    expect(mood?.lastSeenAt).toBe("2026-07-03T00:00:00.000Z");
+    // The day key is the account's local day (default zone, summer time):
+    // its first instant, not the key written out as UTC midnight.
+    expect(mood?.lastSeenAt).toBe("2026-07-02T22:00:00.000Z");
+    expect(mood?.updatedAt).toBe("2026-07-02T22:00:00.000Z");
+  });
+
+  it("puts the mood instant on the logged day for a zone west of UTC", async () => {
+    // The day key as UTC midnight is the previous evening in Los Angeles,
+    // so a client formatting the instant in its own zone showed today's
+    // entry as yesterday's.
+    vi.mocked(getSession).mockResolvedValue({
+      ...SESSION_OK,
+      user: { ...SESSION_OK.user, timezone: "America/Los_Angeles" },
+    } as never);
+    vi.mocked(buildMoodDailySeries).mockResolvedValue({
+      entries: [{ date: "2026-07-03", score: 4, samples: 1 }],
+      summary: null,
+      entryCount: 1,
+      source: "rollup",
+    } as never);
+
+    const res = await callGet(makeReq());
+    const mood = cardsOf(await res.json()).find((c) => c.kind === "mood");
+    const at = new Date(mood?.updatedAt as string);
+    expect(userDayKey(at, "America/Los_Angeles")).toBe("2026-07-03");
+    expect(mood?.updatedAt).toBe("2026-07-03T07:00:00.000Z");
   });
 
   it("omits the mood card when the account has never logged a mood", async () => {
diff --git a/src/app/api/dashboard/summary/route.ts b/src/app/api/dashboard/summary/route.ts
index 084b12087..26d76552f 100644
--- a/src/app/api/dashboard/summary/route.ts
+++ b/src/app/api/dashboard/summary/route.ts
@@ -65,6 +65,7 @@ import { type Locale } from "@/lib/i18n/config";
 import { resolveJobLocale } from "@/lib/i18n/job-locale";
 import { userDayKey, DEFAULT_TIMEZONE } from "@/lib/tz/resolver";
 import { validTimezoneOr } from "@/lib/tz/format";
+import { startOfLocalDayKey } from "@/lib/tz/local-day";
 import { cachedSwr, caches, type ServerCache } from "@/lib/cache/server-cache";
 import { buildMedsTodayBlock } from "@/lib/dashboard/meds-today";
 import { computeStreak } from "@/lib/dashboard/streak";
@@ -879,11 +880,14 @@ async function buildDashboardSummary(
   if (moodSeries.entryCount > 0) {
     const spark = moodSeries.entries.slice(-SPARK_DAYS).map((e) => e.score);
     const latestEntry = moodSeries.entries[moodSeries.entries.length - 1];
-    // The series carries UTC day labels, not timestamps — the entry's day is
-    // the only instant the source actually pins, so it is emitted as the
-    // day's start rather than inventing a reading time.
+    // The series carries the user's LOCAL day keys (`MoodEntry.date`), not
+    // timestamps, so the only honest instant is the first instant of that
+    // day in the user's zone. Writing the key as `T00:00Z` instead put the
+    // instant on the previous calendar day for anyone west of UTC, and a
+    // client formatting it in its own zone showed today's entry as
+    // yesterday's.
     const latestAt = latestEntry
-      ? new Date(`${latestEntry.date}T00:00:00.000Z`).toISOString()
+      ? startOfLocalDayKey(latestEntry.date, userTz).toISOString()
       : null;
     metrics.push({
       id: "mood",
diff --git a/src/lib/openapi/routes/dashboard.ts b/src/lib/openapi/routes/dashboard.ts
index e71ded325..2779f7448 100644
--- a/src/lib/openapi/routes/dashboard.ts
+++ b/src/lib/openapi/routes/dashboard.ts
@@ -223,7 +223,7 @@ const dashboardMetricCard = z
       .datetime({ offset: true })
       .nullable()
       .describe(
-        "Instant behind `latestValue`, falling back to the metric's newest reading. For `mood` this is the day START of the latest daily bucket, not a reading time — the series pins a day, so inventing an instant would be a lie. For `bmi` it is the WEIGHT metadata, since BMI moves exactly when weight does.",
+        "Instant behind `latestValue`, falling back to the metric's newest reading. For `mood` this is the first instant of the latest daily bucket's day in the account's time zone, not a reading time (the series pins a local day, not an instant); formatted in that zone it always lands on the day the entry was logged. For `bmi` it is the WEIGHT metadata, since BMI moves exactly when weight does.",
       ),
     allTimeCount: z
       .number()