fix(dates): read date-only lab and document dates as calendar dates

A date-only value is stored at 12:00 UTC. The lab list and history, the
document cards and pickers, the document date suggestion, extracted
fact dates, source-picker rows and the compliance and mood heatmaps
formatted that instant in the reader's zone, which is the next day from
UTC+12 to UTC+14.

`useCalendarDate` formats such a value through the UTC-pinned calendar
formatter the vaccination list already uses, with the same field order
and locale as instant dates. Lab readings hold both kinds, so
`useLabDate` reads a noon-UTC anchor as its calendar date and a reading
typed with its time of day in the reader's zone. A document without a
filing date shows its upload day, an instant, in the reader's zone.

src/components/charts/compliance-heatmap.tsx

@@ -1,11 +1,8 @@
 "use client";
 
+import { useCalendarDate } from "@/hooks/use-calendar-date";
 import { useState, useMemo, useEffect, useRef } from "react";
-import {
-  useDisplayTimezone,
-  useFormatters,
-  useTranslations,
-} from "@/lib/i18n/context";
+import { useDisplayTimezone, useTranslations } from "@/lib/i18n/context";
 import { heatmapDays } from "@/lib/charts/heatmap-days";
 
 interface DailyData {
@@ -83,12 +80,11 @@ export function ComplianceHeatmap({
   stretch = false,
 }: ComplianceHeatmapProps) {
   const { t } = useTranslations();
-  const fmt = useFormatters();
   const timeZone = useDisplayTimezone();
-  // Day keys are UTC-anchored "YYYY-MM-DD"; format at noon UTC so the
-  // locale-aware renderer never lands a day off in either direction.
-  const formatDay = (dateKey: string) =>
-    fmt.date(new Date(`${dateKey}T12:00:00Z`));
+  // Day keys are calendar dates ("YYYY-MM-DD"), read as such in every zone.
+  // A noon-UTC instant formatted in the reader's zone was a day late from
+  // UTC+12 to UTC+14.
+  const formatDay = useCalendarDate();
   const containerRef = useRef<HTMLDivElement | null>(null);
   const [containerWidth, setContainerWidth] = useState(0);
   const [tooltip, setTooltip] = useState<{

src/components/charts/mood-heatmap.tsx

@@ -1,11 +1,8 @@
 "use client";
 
+import { useCalendarDate } from "@/hooks/use-calendar-date";
 import { useState, useMemo, useEffect, useRef } from "react";
-import {
-  useDisplayTimezone,
-  useFormatters,
-  useTranslations,
-} from "@/lib/i18n/context";
+import { useDisplayTimezone, useTranslations } from "@/lib/i18n/context";
 import { heatmapDays } from "@/lib/charts/heatmap-days";
 import { moodLabelKeyForScore } from "@/lib/mood/labels";
 
@@ -66,12 +63,11 @@ export function MoodHeatmap({
   stretch = false,
 }: MoodHeatmapProps) {
   const { t } = useTranslations();
-  const fmt = useFormatters();
   const timeZone = useDisplayTimezone();
-  // Day keys are UTC-anchored "YYYY-MM-DD"; format at noon UTC so the
-  // locale-aware renderer never lands a day off in either direction.
-  const formatDay = (dateKey: string) =>
-    fmt.date(new Date(`${dateKey}T12:00:00Z`));
+  // Day keys are calendar dates ("YYYY-MM-DD"), read as such in every zone.
+  // A noon-UTC instant formatted in the reader's zone was a day late from
+  // UTC+12 to UTC+14.
+  const formatDay = useCalendarDate();
   const containerRef = useRef<HTMLDivElement | null>(null);
   const [containerWidth, setContainerWidth] = useState(0);
   const [tooltip, setTooltip] = useState<{

src/components/documents/__tests__/document-card-dates.test.tsx

@@ -0,0 +1,106 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { renderToStaticMarkup } from "react-dom/server";
+
+import { makeFormatters } from "@/lib/format-locale";
+import { I18nProvider } from "@/lib/i18n/context";
+import type { InboundDocumentDto } from "@/lib/validations/inbound-documents";
+
+/**
+ * A document's filing date is a calendar date. The card used to anchor it at
+ * 12:00 UTC and format that instant in the reader's zone, which shows the
+ * next day from UTC+12 to UTC+14. A document without a filing date shows its
+ * upload day, an instant, in the reader's zone.
+ *
+ * Server rendering cannot see the reader's profile zone, so the formatter
+ * hook is handed one.
+ */
+const zone = vi.hoisted(() => ({ current: "UTC" }));
+
+vi.mock("@/lib/i18n/context", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("@/lib/i18n/context")>();
+  return {
+    ...actual,
+    useFormatters: () => makeFormatters("en", zone.current, "AUTO", "AUTO"),
+  };
+});
+
+const { DocumentCard } = await import("../document-card");
+
+function doc(overrides: Partial<InboundDocumentDto>): InboundDocumentDto {
+  return {
+    id: "doc-1",
+    kind: "IMAGING",
+    title: "Scan",
+    filename: "scan.pdf",
+    mimeType: "application/pdf",
+    byteSize: 1000,
+    status: "STORED",
+    providerType: null,
+    reportDate: null,
+    documentDate: null,
+    errorReason: null,
+    factCount: 0,
+    pendingCount: 0,
+    conditionLinks: [],
+    encounterLinks: [],
+    servingClass: "inline",
+    hasContentIndex: false,
+    contentIndexSource: null,
+    lastIndexAttemptAt: null,
+    lastIndexOutcome: null,
+    hasThumbnail: false,
+    sourceSystem: null,
+    sourceId: null,
+    createdAt: "2025-10-04T20:30:00.000Z",
+    updatedAt: "2025-10-04T20:30:00.000Z",
+    ...overrides,
+  };
+}
+
+function render(document: InboundDocumentDto) {
+  const noop = () => {};
+  return renderToStaticMarkup(
+    <I18nProvider initialLocale="en">
+      <DocumentCard
+        document={document}
+        selected={false}
+        onToggleSelected={noop}
+        onOpen={noop}
+        highlighted={false}
+      />
+    </I18nProvider>,
+  );
+}
+
+const previousTz = process.env.TZ;
+
+describe("document card dates across zones", () => {
+  afterEach(() => {
+    process.env.TZ = previousTz;
+    zone.current = "UTC";
+  });
+
+  describe.each(["Pacific/Kiritimati", "America/Los_Angeles"])(
+    "in %s",
+    (tz) => {
+      beforeEach(() => {
+        process.env.TZ = tz;
+        zone.current = tz;
+      });
+
+      it("shows the filing date as stated", () => {
+        const html = render(doc({ documentDate: "2025-10-04" }));
+        expect(html).toContain("10/04/2025");
+        expect(html).not.toContain("10/05/2025");
+        expect(html).not.toContain("10/03/2025");
+      });
+    },
+  );
+
+  it("shows the upload day in the reader's zone when no filing date is set", () => {
+    // 20:30 UTC on 4 October is 10:30 on 5 October in Kiritimati.
+    process.env.TZ = "Pacific/Kiritimati";
+    zone.current = "Pacific/Kiritimati";
+    expect(render(doc({ documentDate: null }))).toContain("10/05/2025");
+  });
+});

src/components/documents/document-card.tsx

@@ -16,6 +16,7 @@
  * whole card is clickable through an invisible overlay button; the checkbox
  * floats above it.
  */
+import { useDocumentDate } from "@/components/documents/use-document-date";
 import { Check, Download, Loader2, X } from "lucide-react";
 import { useEffect, useRef, useState } from "react";
 
@@ -24,14 +25,13 @@ import { Button } from "@/components/ui/button";
 import { Card, CardContent } from "@/components/ui/card";
 import { Checkbox } from "@/components/ui/checkbox";
 import { useFencedObjectUrl } from "@/hooks/use-fenced-object-url";
-import { useFormatters, useTranslations } from "@/lib/i18n/context";
+import { useTranslations } from "@/lib/i18n/context";
 import { cn } from "@/lib/utils";
 import type { InboundDocumentDto } from "@/lib/validations/inbound-documents";
 import { DOCUMENT_KIND_ICONS } from "./document-kind-meta";
 import type { UploadQueueItem } from "./use-document-upload";
 import {
   documentCardKeyAction,
-  documentDateKey,
   formatBytes,
   isDocumentProcessing,
 } from "./vault-utils";
@@ -71,7 +71,7 @@ export function DocumentCard({
   onPrefetch?: (id: string) => void;
 }) {
   const { t, locale } = useTranslations();
-  const format = useFormatters();
+  const documentDate = useDocumentDate();
 
   // A preview thumbnail that fails to load (still rendering, decrypt error,
   // 404) falls back to the kind icon — never a broken image.
@@ -101,7 +101,7 @@ export function DocumentCard({
   const title =
     document.title ?? document.filename ?? t("documents.card.untitled");
   const Icon = DOCUMENT_KIND_ICONS[document.kind];
-  const date = format.date(`${documentDateKey(document)}T12:00:00.000Z`);
+  const date = documentDate(document);
   const size = formatBytes(document.byteSize, locale);
   const showFilename =
     document.filename !== null && document.filename !== title;

src/components/documents/document-detail-sheet.tsx

@@ -16,6 +16,7 @@
  * copy. A Share action in the footer opens the clinician share-link create
  * flow (shared `ShareLinkCreateForm`) with this document pre-attached.
  */
+import { useCalendarDate } from "@/hooks/use-calendar-date";
 import { useRecordCapabilities } from "@/hooks/use-record-capabilities";
 import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import {
@@ -344,6 +345,7 @@ export function DocumentDetailSheet({
 }) {
   const { t, tCount, locale } = useTranslations();
   const format = useFormatters();
+  const calendarDate = useCalendarDate();
   const queryClient = useQueryClient();
   // v1.28.52 (Documents R3) — the vault "Ask the Coach" action opens the REAL
   // fenced coach conversation in the shared side drawer (scoped to this
@@ -695,7 +697,7 @@ export function DocumentDetailSheet({
     ? t(`documents.kind.${suggestion.kind}`)
     : null;
   const suggestionDateLabel = suggestion?.documentDate
-    ? format.date(`${suggestion.documentDate}T12:00:00.000Z`)
+    ? calendarDate(suggestion.documentDate)
     : null;
 
   const title = doc?.title ?? doc?.filename ?? t("documents.card.untitled");

src/components/documents/document-facts-review.tsx

@@ -24,6 +24,7 @@
  * rejected (stated in the copy); an unverified low-confidence fact gets NO
  * decision and stays pending rather than being silently discarded.
  */
+import { useCalendarDate } from "@/hooks/use-calendar-date";
 import { useState } from "react";
 import { FlaskConical, Loader2, ScanSearch } from "lucide-react";
 import { toast } from "sonner";
@@ -34,7 +35,7 @@ import { Checkbox } from "@/components/ui/checkbox";
 import { DateField } from "@/components/ui/date-field";
 import { Input } from "@/components/ui/input";
 import { Label } from "@/components/ui/label";
-import { useFormatters, useTranslations } from "@/lib/i18n/context";
+import { useTranslations } from "@/lib/i18n/context";
 import { cn } from "@/lib/utils";
 import type {
   ConditionFactData,
@@ -209,7 +210,7 @@ function FactRow({
   failure: string | null;
 }) {
   const { t } = useTranslations();
-  const format = useFormatters();
+  const calendarDate = useCalendarDate();
   const editFact = useEditFact();
   const [verifying, setVerifying] = useState(false);
   const [draft, setDraft] = useState<VerifyDraft>(() => draftFor(fact));
@@ -260,7 +261,7 @@ function FactRow({
           </p>
           <p className="text-muted-foreground text-xs">
             {typeLabel}
-            {date ? ` · ${format.date(`${date}T12:00:00.000Z`)}` : ""}
+            {date ? ` · ${calendarDate(date)}` : ""}
             {isObservation &&
             (fact.data as ObservationFactData).referenceText ? (
               <>

src/components/documents/document-link-picker.tsx

@@ -12,6 +12,7 @@
  * Shows one page (50) of matches — the search input is the way to reach an
  * older document, mirroring the vault's own recall model.
  */
+import { useDocumentDate } from "@/components/documents/use-document-date";
 import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import { Check, Search } from "lucide-react";
 import { useEffect, useRef, useState } from "react";
@@ -22,7 +23,7 @@ import { ResponsiveSheet } from "@/components/ui/responsive-sheet";
 import { Skeleton } from "@/components/ui/skeleton";
 import { QueryErrorRow } from "@/components/ui/query-error-row";
 import { apiGet, apiPost } from "@/lib/api/api-fetch";
-import { useFormatters, useTranslations } from "@/lib/i18n/context";
+import { useTranslations } from "@/lib/i18n/context";
 import { invalidateKeys, queryKeys } from "@/lib/query-keys";
 import { cn } from "@/lib/utils";
 import type {
@@ -30,7 +31,6 @@ import type {
   InboundDocumentDto,
 } from "@/lib/validations/inbound-documents";
 import { DOCUMENT_KIND_ICONS } from "./document-kind-meta";
-import { documentDateKey } from "./vault-utils";
 
 interface ListPage {
   documents: InboundDocumentDto[];
@@ -47,7 +47,7 @@ export function DocumentLinkPicker({
   onOpenChange: (open: boolean) => void;
 }) {
   const { t } = useTranslations();
-  const format = useFormatters();
+  const documentDate = useDocumentDate();
   const queryClient = useQueryClient();
 
   const [searchDraft, setSearchDraft] = useState("");
@@ -174,7 +174,7 @@ export function DocumentLinkPicker({
                         {title}
                       </span>
                       <span className="text-muted-foreground block text-xs">
-                        {format.date(`${documentDateKey(doc)}T12:00:00.000Z`)}
+                        {documentDate(doc)}
                       </span>
                     </span>
                     <Check

src/components/documents/episode-documents-card.tsx

@@ -14,6 +14,7 @@
  * module-gated surfaces never leak. An episode without documents shows a
  * quiet one-line affordance, not a teaching empty state.
  */
+import { useDocumentDate } from "@/components/documents/use-document-date";
 import { useQuery } from "@tanstack/react-query";
 import { FolderOpen, Link2, Upload } from "lucide-react";
 import Link from "next/link";
@@ -28,13 +29,12 @@ import { Skeleton } from "@/components/ui/skeleton";
 import { useAuth } from "@/hooks/use-auth";
 import { useRecordCapabilities } from "@/hooks/use-record-capabilities";
 import { apiGet } from "@/lib/api/api-fetch";
-import { useFormatters, useTranslations } from "@/lib/i18n/context";
+import { useTranslations } from "@/lib/i18n/context";
 import { queryKeys } from "@/lib/query-keys";
 import type { InboundDocumentDto } from "@/lib/validations/inbound-documents";
 import { DocumentLinkPicker } from "./document-link-picker";
 import { ImportFromSourceButton } from "./sources/import-from-source-button";
 import { DOCUMENT_KIND_ICONS } from "./document-kind-meta";
-import { documentDateKey } from "./vault-utils";
 
 /** Compact preview size — "Alle anzeigen" carries the long tail. */
 const PREVIEW_LIMIT = 5;
@@ -46,7 +46,7 @@ interface ListPage {
 
 export function EpisodeDocumentsCard({ episodeId }: { episodeId: string }) {
   const { t } = useTranslations();
-  const format = useFormatters();
+  const documentDate = useDocumentDate();
   const { user } = useAuth();
   // Linking a document to an episode writes through
   // `POST /api/documents/inbound/bulk`, the same endpoint the vault gates on
@@ -137,7 +137,7 @@ export function EpisodeDocumentsCard({ episodeId }: { episodeId: string }) {
                           {title}
                         </span>
                         <span className="text-muted-foreground shrink-0 text-xs">
-                          {format.date(`${documentDateKey(doc)}T12:00:00.000Z`)}
+                          {documentDate(doc)}
                         </span>
                       </Link>
                     </ListRow>

src/components/documents/sources/document-source-picker.tsx

@@ -27,6 +27,7 @@
  * With either, a document already in HealthLog can be picked too: it is not
  * stored twice, it is linked or handed to the form.
  */
+import { useCalendarDate } from "@/hooks/use-calendar-date";
 import {
   useInfiniteQuery,
   useQuery,
@@ -66,7 +67,7 @@ import {
   type DocumentSourceSearchDto,
   type DocumentSourceTagDto,
 } from "@/lib/documents/sources/types";
-import { useFormatters, useTranslations } from "@/lib/i18n/context";
+import { useTranslations } from "@/lib/i18n/context";
 import { invalidateKeys, queryKeys } from "@/lib/query-keys";
 import { cn } from "@/lib/utils";
 import type { InboundDocumentKindValue } from "@/lib/validations/inbound-documents";
@@ -119,7 +120,7 @@ export function DocumentSourcePicker({
   onImported,
 }: DocumentSourcePickerProps) {
   const { t, locale } = useTranslations();
-  const format = useFormatters();
+  const calendarDate = useCalendarDate();
   const queryClient = useQueryClient();
 
   const [system, setSystem] = useState<DocumentPickerSystem | null>(null);
@@ -581,7 +582,7 @@ export function DocumentSourcePicker({
               const run = runs.get(row.sourceId);
               const allowed = selectable(row);
               const meta = [
-                row.date ? format.date(`${row.date}T12:00:00.000Z`) : null,
+                row.date ? calendarDate(row.date) : null,
                 row.sizeBytes !== null
                   ? formatBytes(row.sizeBytes, locale)
                   : null,

src/components/documents/use-document-date.ts

@@ -0,0 +1,27 @@
+"use client";
+
+import { useCallback } from "react";
+
+import { useCalendarDate } from "@/hooks/use-calendar-date";
+import { useFormatters } from "@/lib/i18n/context";
+import type { InboundDocumentDto } from "@/lib/validations/inbound-documents";
+
+/**
+ * The date a document files under, as a reader sees it. A filing date is a
+ * calendar date and reads the same in every zone; a document without one
+ * shows the day it was uploaded, which is an instant and reads in the
+ * reader's zone.
+ */
+export function useDocumentDate(): (
+  doc: Pick<InboundDocumentDto, "documentDate" | "createdAt">,
+) => string {
+  const fmt = useFormatters();
+  const calendarDate = useCalendarDate();
+  return useCallback(
+    (doc) =>
+      doc.documentDate
+        ? calendarDate(doc.documentDate)
+        : fmt.date(doc.createdAt),
+    [fmt, calendarDate],
+  );
+}

src/components/labs/__tests__/lab-history-dates.test.tsx

@@ -0,0 +1,110 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { renderToStaticMarkup } from "react-dom/server";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+
+import { makeFormatters } from "@/lib/format-locale";
+import { I18nProvider } from "@/lib/i18n/context";
+import type { LabResultDto } from "../types";
+
+/**
+ * A reading imported from a report that states only its date is stored at
+ * 12:00 UTC. Formatted in the reader's zone it read as the next day from
+ * UTC+12 to UTC+14. A reading typed with its time of day is an instant and
+ * keeps reading in the reader's zone.
+ *
+ * Server rendering cannot see the reader's profile zone, so the test hands
+ * it over the two ways the app reads it: the formatter hook and the
+ * mirrored zone the legacy helpers read.
+ */
+const zone = vi.hoisted(() => ({ current: "UTC" }));
+
+vi.mock("@/lib/timezone-mirror", async (importOriginal) => ({
+  ...(await importOriginal<typeof import("@/lib/timezone-mirror")>()),
+  readStoredTimezone: () => zone.current,
+}));
+vi.mock("@/lib/i18n/context", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("@/lib/i18n/context")>();
+  return {
+    ...actual,
+    useFormatters: () => makeFormatters("en", zone.current, "AUTO", "AUTO"),
+  };
+});
+vi.mock("@/lib/api/api-fetch", () => ({
+  apiGet: () => new Promise(() => {}),
+  apiDelete: vi.fn(),
+  apiPost: vi.fn(),
+  apiPut: vi.fn(),
+}));
+
+const { LabHistoryList } = await import("../lab-history-list");
+
+function reading(id: string, takenAt: string): LabResultDto {
+  return {
+    id,
+    biomarkerId: "bm-1",
+    panel: null,
+    analyte: "TSH",
+    value: 1.8,
+    valueText: null,
+    unit: "mIU/L",
+    referenceLow: 0.4,
+    referenceHigh: 4,
+    catalogReferenceLow: 0.4,
+    catalogReferenceHigh: 4,
+    sourceReferenceLow: null,
+    sourceReferenceHigh: null,
+    sourceReferenceText: null,
+    referenceOrigin: "catalog",
+    referenceDivergesFromCatalog: false,
+    takenAt,
+    source: "MANUAL",
+    hasNote: false,
+    rangeStatus: "in-range",
+    createdAt: takenAt,
+    updatedAt: takenAt,
+  } as LabResultDto;
+}
+
+function render(readings: LabResultDto[]) {
+  return renderToStaticMarkup(
+    <QueryClientProvider client={new QueryClient()}>
+      <I18nProvider initialLocale="en">
+        <LabHistoryList readings={readings} />
+      </I18nProvider>
+    </QueryClientProvider>,
+  );
+}
+
+const previousTz = process.env.TZ;
+
+describe("lab reading dates across zones", () => {
+  afterEach(() => {
+    process.env.TZ = previousTz;
+    zone.current = "UTC";
+  });
+
+  describe.each(["Pacific/Kiritimati", "America/Los_Angeles"])(
+    "in %s",
+    (tz) => {
+      beforeEach(() => {
+        process.env.TZ = tz;
+        zone.current = tz;
+      });
+
+      it("shows a date-only reading on its stated date", () => {
+        const html = render([reading("r1", "2025-10-04T12:00:00.000Z")]);
+        expect(html).toContain("10/04/2025");
+        expect(html).not.toContain("10/05/2025");
+        expect(html).not.toContain("10/03/2025");
+      });
+    },
+  );
+
+  it("dates a reading typed with its time of day in the reader's zone", () => {
+    // 20:30 UTC on 4 October is 10:30 on 5 October in Kiritimati.
+    process.env.TZ = "Pacific/Kiritimati";
+    zone.current = "Pacific/Kiritimati";
+    const html = render([reading("r1", "2025-10-04T20:30:00.000Z")]);
+    expect(html).toContain("10/05/2025");
+  });
+});

src/components/labs/lab-history-list.tsx

@@ -28,7 +28,6 @@ import { Textarea } from "@/components/ui/textarea";
 import { useTableSort } from "@/hooks/use-table-sort";
 import { apiDelete, apiGet, apiPost, apiPut } from "@/lib/api/api-fetch";
 import { localizedApiError } from "@/lib/api/localized-error";
-import { formatDateShort } from "@/lib/format";
 import { formatLabReading } from "@/lib/labs/format-value";
 import { resolveNoteForUpdate } from "@/lib/labs/note-update";
 import { useTranslations } from "@/lib/i18n/context";
@@ -38,7 +37,7 @@ import { ReferenceRangeBadge } from "./reference-range-badge";
 import { LabReferenceRangeBar } from "./lab-reference-range-bar";
 import { SourceRangeNote } from "./source-range-note";
 import type { LabResultDetailDto, LabResultDto } from "./types";
-import { useLabNumber } from "./use-lab-format";
+import { useLabDate, useLabNumber } from "./use-lab-format";
 
 const NOTE_MAX_LENGTH = 2000;
 
@@ -79,6 +78,7 @@ function parseDecimal(raw: string): number | null {
 export function LabHistoryList({ readings }: { readings: LabResultDto[] }) {
   const { t } = useTranslations();
   const labNumber = useLabNumber();
+  const labDate = useLabDate();
   const { canManageDomain } = useRecordCapabilities();
   const canManageLabs = canManageDomain("labs");
   const queryClient = useQueryClient();
@@ -364,9 +364,7 @@ export function LabHistoryList({ readings }: { readings: LabResultDto[] }) {
                 unit={r.unit}
               />
               <div className="text-muted-foreground flex flex-wrap items-center gap-x-2 gap-y-1 text-sm">
-                <span className="whitespace-nowrap">
-                  {formatDateShort(r.takenAt, true)}
-                </span>
+                <span className="whitespace-nowrap">{labDate(r.takenAt)}</span>
                 <ReferenceRangeBadge status={r.rangeStatus} />
                 {r.hasNote ? (
                   <span className="text-xs">{t("labs.hasNote")}</span>
@@ -433,7 +431,7 @@ export function LabHistoryList({ readings }: { readings: LabResultDto[] }) {
                   </div>
                 </TableCell>
                 <TableCell className="text-muted-foreground text-sm whitespace-nowrap">
-                  {formatDateShort(r.takenAt, true)}
+                  {labDate(r.takenAt)}
                 </TableCell>
                 <TableCell>
                   <div className="flex flex-col items-start gap-1">

src/components/labs/lab-list.tsx

@@ -13,7 +13,6 @@ import { EmptyState } from "@/components/ui/empty-state";
 import { QueryErrorCard } from "@/components/ui/query-error-card";
 import { Skeleton } from "@/components/ui/skeleton";
 import { apiGet } from "@/lib/api/api-fetch";
-import { formatDate } from "@/lib/format";
 import { formatReferenceRange } from "@/lib/labs/reference-range";
 import { formatLabReading } from "@/lib/labs/format-value";
 import { useTranslations } from "@/lib/i18n/context";
@@ -22,7 +21,7 @@ import { queryKeys } from "@/lib/query-keys";
 import { applyOrder, useModuleListPrefs } from "@/lib/module-list-prefs";
 
 import { LabTrendSparkline } from "./lab-trend-sparkline";
-import { useLabNumber } from "./use-lab-format";
+import { useLabDate, useLabNumber } from "./use-lab-format";
 import { LabReferenceRangeBar } from "./lab-reference-range-bar";
 import { ReferenceRangeBadge } from "./reference-range-badge";
 import { SourceRangeNote } from "./source-range-note";
@@ -124,6 +123,7 @@ const MOBILE_CELL = {
 export function LabList({ onAddFirst }: { onAddFirst?: () => void } = {}) {
   const { t } = useTranslations();
   const labNumber = useLabNumber();
+  const labDate = useLabDate();
   const { canWriteDomain } = useRecordCapabilities();
   const canAddLab = canWriteDomain("labs");
   const { prefs } = useModuleListPrefs("labs");
@@ -259,7 +259,7 @@ export function LabList({ onAddFirst }: { onAddFirst?: () => void } = {}) {
                     <span className="text-foreground font-semibold tabular-nums">
                       {formatLabReading(group.latest, labNumber)}
                     </span>
-                    <span>{formatDate(group.latest.takenAt)}</span>
+                    <span>{labDate(group.latest.takenAt)}</span>
                   </div>
                 </div>
               );
@@ -394,7 +394,7 @@ export function LabList({ onAddFirst }: { onAddFirst?: () => void } = {}) {
                       className="text-xs"
                     />
                     <span className="text-xs">
-                      {formatDate(group.latest.takenAt)}
+                      {labDate(group.latest.takenAt)}
                     </span>
                     {group.readings.length > 1 ? (
                       <span className="text-xs">

src/components/labs/use-lab-format.ts

@@ -2,8 +2,10 @@
 
 import { useCallback } from "react";
 
+import { useCalendarDate } from "@/hooks/use-calendar-date";
 import { useFormatters } from "@/lib/i18n/context";
 import { formatLabValue, type LabNumberFormat } from "@/lib/labs/format-value";
+import { isNoonUtcAnchor } from "@/lib/tz/date-only";
 
 /**
  * A lab value in the reader's number format, trimmed the way every lab
@@ -16,3 +18,23 @@ export function useLabNumber(): LabNumberFormat {
     [fmt],
   );
 }
+
+/**
+ * The date a lab reading was taken. A reading entered by hand carries its
+ * time of day and is dated in the reader's zone; one imported from a report
+ * that states only the date is stored at noon UTC and is dated by that
+ * calendar date, so it does not move to the next day east of UTC+12.
+ */
+export function useLabDate(): (takenAt: string) => string {
+  const fmt = useFormatters();
+  const calendarDate = useCalendarDate();
+  return useCallback(
+    (takenAt: string) => {
+      const instant = new Date(takenAt);
+      return isNoonUtcAnchor(instant)
+        ? calendarDate(instant)
+        : fmt.date(instant);
+    },
+    [fmt, calendarDate],
+  );
+}

src/components/settings/share-document-picker.tsx

@@ -13,6 +13,7 @@
  * the central factory; reads unwrap `(await res.json()).data` via `apiGet`.
  * No write happens here — attaching is the create mutation's job.
  */
+import { useDocumentDate } from "@/components/documents/use-document-date";
 import { useQuery } from "@tanstack/react-query";
 import { Check, Search } from "lucide-react";
 import { useEffect, useRef, useState } from "react";
@@ -23,9 +24,8 @@ import { QueryErrorRow } from "@/components/ui/query-error-row";
 import { ResponsiveSheet } from "@/components/ui/responsive-sheet";
 import { Skeleton } from "@/components/ui/skeleton";
 import { DOCUMENT_KIND_ICONS } from "@/components/documents/document-kind-meta";
-import { documentDateKey } from "@/components/documents/vault-utils";
 import { apiGet } from "@/lib/api/api-fetch";
-import { useFormatters, useTranslations } from "@/lib/i18n/context";
+import { useTranslations } from "@/lib/i18n/context";
 import { queryKeys } from "@/lib/query-keys";
 import { cn } from "@/lib/utils";
 import type { InboundDocumentDto } from "@/lib/validations/inbound-documents";
@@ -55,7 +55,7 @@ export function ShareDocumentPicker({
   max: number;
 }) {
   const { t } = useTranslations();
-  const format = useFormatters();
+  const documentDate = useDocumentDate();
 
   const [searchDraft, setSearchDraft] = useState("");
   const [query, setQuery] = useState("");
@@ -195,7 +195,7 @@ export function ShareDocumentPicker({
                         {title}
                       </span>
                       <span className="text-muted-foreground block text-xs">
-                        {format.date(`${documentDateKey(doc)}T12:00:00.000Z`)}
+                        {documentDate(doc)}
                       </span>
                     </span>
                     <Check

src/hooks/use-calendar-date.ts

@@ -0,0 +1,32 @@
+"use client";
+
+import { useCallback } from "react";
+
+import { formatDate } from "@/lib/date-format";
+import { useDateFormatPreference, useTranslations } from "@/lib/i18n/context";
+
+/**
+ * Format a date-only value: a `YYYY-MM-DD` key, or a stored instant that
+ * stands for a calendar date (noon UTC, or a `@db.Date` column's UTC
+ * midnight). The calendar date is read in UTC, so it is the same day in
+ * every zone.
+ *
+ * Formatting such a value in the reader's zone is how a noon-UTC date came
+ * to show the next day from UTC+12 to UTC+14. Same field order and locale as
+ * `useFormatters().date`, so it sits beside instant-formatted dates without
+ * looking different.
+ */
+export function useCalendarDate(): (value: string | Date) => string {
+  const { locale } = useTranslations();
+  const dateFormat = useDateFormatPreference();
+  return useCallback(
+    (value: string | Date) =>
+      formatDate(
+        // `formatDate` reads a bare key as a calendar date already.
+        typeof value === "string" ? value.slice(0, 10) : value,
+        dateFormat,
+        locale,
+      ),
+    [dateFormat, locale],
+  );
+}

src/lib/tz/__tests__/date-only.test.ts

@@ -1,5 +1,6 @@
 import { describe, expect, it } from "vitest";
 import {
+  isNoonUtcAnchor,
   dateOnlyAtNoonUtc,
   dateOnlyKey,
   dayKeyAsUtcMidnight,
@@ -50,3 +51,12 @@ describe("calendar key arithmetic", () => {
     expect(weekdayOfDateKey("2026-10-04")).toBe(0); // Sunday
   });
 });
+
+describe("isNoonUtcAnchor", () => {
+  it("recognises the stored anchor of a date-only value and nothing else", () => {
+    expect(isNoonUtcAnchor(dateOnlyAtNoonUtc("2025-10-04"))).toBe(true);
+    expect(isNoonUtcAnchor(new Date("2025-10-04T12:00:01.000Z"))).toBe(false);
+    expect(isNoonUtcAnchor(new Date("2025-10-04T00:00:00.000Z"))).toBe(false);
+    expect(isNoonUtcAnchor(new Date("2025-10-04T20:30:00.000Z"))).toBe(false);
+  });
+});

src/lib/tz/date-only.ts

@@ -58,6 +58,24 @@ export function dateOnlyAtNoonUtc(key: string): Date {
   return new Date(`${key}T12:00:00.000Z`);
 }
 
+/**
+ * True when a stored instant is the noon-UTC anchor of a date-only value.
+ *
+ * For a column that holds both kinds (a lab reading typed with its time of
+ * day, or imported from a report that states only the date), this is how a
+ * reader tells them apart. A reading typed at exactly 12:00:00.000 UTC reads
+ * as its UTC calendar date, which is its local date everywhere from UTC-11
+ * to UTC+11.
+ */
+export function isNoonUtcAnchor(value: Date): boolean {
+  return (
+    value.getUTCHours() === 12 &&
+    value.getUTCMinutes() === 0 &&
+    value.getUTCSeconds() === 0 &&
+    value.getUTCMilliseconds() === 0
+  );
+}
+
 /**
  * The calendar date of a stored date-only value (or of a `@db.Date` column,
  * which Prisma hands back as UTC midnight). Only for values that ARE dates: