diff --git a/src/__tests__/timezone-explicit-formatter-guard.test.ts b/src/__tests__/timezone-explicit-formatter-guard.test.ts
index 9eaf1456e..ee2bff254 100644
--- a/src/__tests__/timezone-explicit-formatter-guard.test.ts
+++ b/src/__tests__/timezone-explicit-formatter-guard.test.ts
@@ -51,6 +51,11 @@ const ALLOWLIST: ReadonlyArray<{ file: string; why: string }> = [
 const FORMATTER_PATTERNS = [
   /new Intl\.DateTimeFormat\s*\(/g,
   /\.toLocale(?:Date|Time)String\s*\(/g,
+  // The shared cache's own entry point: it forwards its options straight to
+  // `Intl.DateTimeFormat`, so a call that omits the zone is a bare formatter
+  // exactly like the constructor form (the workout surfaces did this until
+  // v1.43.6).
+  /\bgetDateTimeFormat\s*\(/g,
 ];
 
 /** The argument list starting at the `(` at or after `from`. */
@@ -68,12 +73,30 @@ function argumentList(source: string, from: number): string {
   return source.slice(open);
 }
 
+/** Number of top-level, comma-separated arguments in `(…)`. */
+function topLevelArgCount(args: string): number {
+  let depth = 0;
+  let count = 0;
+  let sawContent = false;
+  for (const ch of args.slice(1, -1)) {
+    if ("([{".includes(ch)) depth += 1;
+    else if (")]}".includes(ch)) depth -= 1;
+    else if (ch === "," && depth === 0) {
+      count += 1;
+      sawContent = false;
+      continue;
+    }
+    if (!/\s/.test(ch)) sawContent = true;
+  }
+  return sawContent ? count + 1 : count;
+}
+
 function bareFormatterSites(): Array<{ file: string; line: number }> {
   const listed = execFileSync(
     "grep",
     [
       "-rlE",
-      "new Intl\\.DateTimeFormat|\\.toLocale(Date|Time)String\\(",
+      "new Intl\\.DateTimeFormat|\\.toLocale(Date|Time)String\\(|getDateTimeFormat\\(",
       "src",
       "--include=*.ts",
       "--include=*.tsx",
@@ -105,6 +128,15 @@ function bareFormatterSites(): Array<{ file: string; line: number }> {
         // of them and the honest response would be to allowlist them — which
         // is how a guard stops guarding.
         if (/\btimeZone\s*(?::|,|\}|$)/m.test(args)) continue;
+        // `getDateTimeFormat(locale, tz, options)` takes the zone as its own
+        // argument; only the two-argument `(locale, options)` form can leave
+        // it out.
+        if (m[0].startsWith("getDateTimeFormat") && topLevelArgCount(args) >= 3)
+          continue;
+        // A mention in a comment renders nothing.
+        const lineStart = source.lastIndexOf("\n", m.index) + 1;
+        if (/^\s*(?:\/\/|\*|\/\*)/.test(source.slice(lineStart, m.index)))
+          continue;
         hits.push({
           file,
           line: source.slice(0, m.index).split("\n").length,
@@ -125,7 +157,7 @@ describe("date formatters name the calendar they render in", () => {
       "grep",
       [
         "-rlE",
-        "new Intl\\.DateTimeFormat|\\.toLocale(Date|Time)String\\(",
+        "new Intl\\.DateTimeFormat|\\.toLocale(Date|Time)String\\(|getDateTimeFormat\\(",
         "src",
         "--include=*.ts",
         "--include=*.tsx",
diff --git a/src/components/dashboard/recent-workouts-tile.tsx b/src/components/dashboard/recent-workouts-tile.tsx
index 60c094a15..ec0f87625 100644
--- a/src/components/dashboard/recent-workouts-tile.tsx
+++ b/src/components/dashboard/recent-workouts-tile.tsx
@@ -4,7 +4,7 @@ import Link from "next/link";
 import { Activity } from "lucide-react";
 
 import { formatDurationMinutes } from "@/lib/i18n/duration";
-import { useTranslations } from "@/lib/i18n/context";
+import { useDisplayTimezone, useTranslations } from "@/lib/i18n/context";
 import { useWorkouts, type WorkoutListEntry } from "@/hooks/use-workouts";
 import { cn } from "@/lib/utils";
 import { Card, CardContent, CardHeader } from "@/components/ui/card";
@@ -32,9 +32,10 @@ import { iconForSport } from "@/lib/workouts/sport-icons";
  * round-trip per session.
  */
 
-function formatDayLabel(iso: string, locale: string): string {
+function formatDayLabel(iso: string, locale: string, timeZone: string): string {
   const d = new Date(iso);
   return getDateTimeFormat(locale, {
+    timeZone,
     weekday: "short",
     day: "2-digit",
     month: "short",
@@ -61,6 +62,7 @@ function renderRow(workout: WorkoutListEntry, sportName: string) {
 
 export function RecentWorkoutsTile() {
   const { t, locale } = useTranslations();
+  const timeZone = useDisplayTimezone();
   const { data, isError, refetch } = useWorkouts({ limit: 3 });
 
   // A query's `isLoading` is not a hydration-safe branch: TanStack reports the
@@ -145,7 +147,7 @@ export function RecentWorkoutsTile() {
                   >
                     {renderRow(workout, sportName)}
                     <span className="text-muted-foreground shrink-0 text-xs tabular-nums">
-                      {formatDayLabel(workout.startedAt, locale)}
+                      {formatDayLabel(workout.startedAt, locale, timeZone)}
                     </span>
                     <span className="ml-1 shrink-0 text-xs font-medium tabular-nums">
                       {formatDurationMinutes(
diff --git a/src/components/insights/workout-detail/format.ts b/src/components/insights/workout-detail/format.ts
index a3027ea5d..443ab5cd9 100644
--- a/src/components/insights/workout-detail/format.ts
+++ b/src/components/insights/workout-detail/format.ts
@@ -126,16 +126,19 @@ export function formatDateRange(
   endedAt: string,
   locale: string,
   timeFormat: TimeFormatPreference,
+  timeZone: string,
 ): string {
   const start = new Date(startedAt);
   const end = new Date(endedAt);
   const dateFmt = getDateTimeFormat(locale, {
+    timeZone,
     weekday: "long",
     day: "2-digit",
     month: "long",
     year: "numeric",
   });
   const timeFmt = getDateTimeFormat(locale, {
+    timeZone,
     hour: "2-digit",
     minute: "2-digit",
     ...hourCycleOptions(timeFormat),
diff --git a/src/components/insights/workout-detail/header.tsx b/src/components/insights/workout-detail/header.tsx
index 1e4200f0b..b82c6e218 100644
--- a/src/components/insights/workout-detail/header.tsx
+++ b/src/components/insights/workout-detail/header.tsx
@@ -1,6 +1,10 @@
 "use client";
 
-import { useTranslations, useTimeFormatPreference } from "@/lib/i18n/context";
+import {
+  useDisplayTimezone,
+  useTimeFormatPreference,
+  useTranslations,
+} from "@/lib/i18n/context";
 import { MEASUREMENT_SOURCE_LIST_LABEL_KEYS } from "@/lib/i18n/source-labels";
 import { iconForSport } from "@/lib/workouts/sport-icons";
 import type { WorkoutDetailPayload } from "@/hooks/use-workouts";
@@ -32,6 +36,7 @@ function renderSportIconBadge(sportType: string) {
 export function WorkoutDetailHeader({ workout }: WorkoutDetailHeaderProps) {
   const { t, locale } = useTranslations();
   const timeFormat = useTimeFormatPreference();
+  const timeZone = useDisplayTimezone();
   const { preference } = useUnitDisplay();
   const sportLabelKey = `insights.workouts.sport.${workout.sportType}`;
   const sportLabel = t(sportLabelKey);
@@ -68,6 +73,7 @@ export function WorkoutDetailHeader({ workout }: WorkoutDetailHeaderProps) {
               workout.endedAt,
               locale,
               timeFormat,
+              timeZone,
             )}
           </p>
         </div>
diff --git a/src/components/insights/workout-list.tsx b/src/components/insights/workout-list.tsx
index 913a19846..3ca14f2fc 100644
--- a/src/components/insights/workout-list.tsx
+++ b/src/components/insights/workout-list.tsx
@@ -7,7 +7,11 @@ import { HeartPulse, Loader2, Map as MapIcon } from "lucide-react";
 import { cn } from "@/lib/utils";
 import { getNumberFormat, getDateTimeFormat } from "@/lib/intl/formatter-cache";
 import { formatDurationMinutes } from "@/lib/i18n/duration";
-import { useTranslations, useTimeFormatPreference } from "@/lib/i18n/context";
+import {
+  useDisplayTimezone,
+  useTimeFormatPreference,
+  useTranslations,
+} from "@/lib/i18n/context";
 import {
   hourCycleOptions,
   type TimeFormatPreference,
@@ -40,12 +44,16 @@ function formatDate(
   iso: string,
   locale: string,
   timeFormat: TimeFormatPreference,
+  timeZone: string,
 ): string {
   const d = new Date(iso);
   // Show the year whenever the workout is not from the current year, so a
   // "Do., 16. Dez." from a previous year is never mistaken for this year's.
-  const showYear = d.getFullYear() !== new Date().getFullYear();
+  const yearOf = (value: Date) =>
+    getDateTimeFormat(locale, { timeZone, year: "numeric" }).format(value);
+  const showYear = yearOf(d) !== yearOf(new Date());
   return getDateTimeFormat(locale, {
+    timeZone,
     weekday: "short",
     day: "2-digit",
     month: "short",
@@ -75,6 +83,7 @@ export function WorkoutList({
 }: WorkoutListProps) {
   const { t, locale } = useTranslations();
   const timeFormat = useTimeFormatPreference();
+  const timeZone = useDisplayTimezone();
   const { preference } = useUnitDisplay();
 
   return (
@@ -141,7 +150,12 @@ export function WorkoutList({
                     stays readable beside the stats column. */}
                 <span className="text-muted-foreground text-xs">
                   <DayLinkAt at={workout.startedAt} className="z-10">
-                    {formatDate(workout.startedAt, locale, timeFormat)}
+                    {formatDate(
+                      workout.startedAt,
+                      locale,
+                      timeFormat,
+                      timeZone,
+                    )}
                   </DayLinkAt>
                 </span>
               </div>
diff --git a/src/lib/format-locale.ts b/src/lib/format-locale.ts
index 5186efdf0..68548ea40 100644
--- a/src/lib/format-locale.ts
+++ b/src/lib/format-locale.ts
@@ -124,9 +124,12 @@ function asDate(value: DateInput): Date {
  * lookup is cheap.
  */
 function isCurrentYearInTz(date: Date, tz: string, localeTag: string): boolean {
-  const yearOnly = { timeZone: tz, year: "numeric" as const };
-  const target = getDateTimeFormat(localeTag, yearOnly).format(date);
-  const now = getDateTimeFormat(localeTag, yearOnly).format(new Date());
+  const yearIn = (value: Date) =>
+    getDateTimeFormat(localeTag, { timeZone: tz, year: "numeric" }).format(
+      value,
+    );
+  const target = yearIn(date);
+  const now = yearIn(new Date());
   return target === now;
 }