fix(dates): show the year whenever a date is not the current one

Sweeps every surface that renders a date from before this year without
a year suffix — illness episodes/flares/day-logs, lab and custom-metric
charts, the mood chart family, medication titration/side-effects/dose-
history/next-dose captions (incl. the Dec→Jan rollover), cycle
predictions and history, the BBT chart, the intraday-pulse day-nav, the
date-range filter chip, and the nutrient/compliance charts. Each now
routes through dateShortSmart / dateWithWeekdaySmart (format-locale.ts)
or the matching date-format.ts helper, which add the year only when it
differs from the current one — mirroring the workout list's existing
model instead of a bare "19.02." that reads as this year's.

Also fixes two sites that bypassed the app's locale entirely: the
trusted-devices expiry (bare toLocaleDateString, host locale) and the
admin token-name timestamp (hard-coded de-DE + Europe/Berlin) now both
render through the user's own locale, hour-cycle, and timezone
preference.

src/components/admin/api-token-overview-section.tsx

@@ -11,10 +11,11 @@ import {
   TooltipTrigger,
 } from "@/components/ui/tooltip";
 import { formatDate, formatDateTime } from "@/lib/format";
+import type { Formatters } from "@/lib/format-locale";
 import { SettingsCard } from "@/components/settings/settings-card";
 import { SettingsCardHeader } from "@/components/settings/_card-header";
 import { ListRow } from "@/components/ui/list-row";
-import { useTranslations } from "@/lib/i18n/context";
+import { useTranslations, useFormatters } from "@/lib/i18n/context";
 import { queryKeys } from "@/lib/query-keys";
 import { type ApiTokenInfo } from "./_shared";
 import { apiGet } from "@/lib/api/api-fetch";
@@ -114,35 +115,30 @@ function TokenStatusBadge({
 const TOKEN_NAME_ISO_RE =
   /^(.+?)\s+(\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(?:\.\d+)?(?:Z|[+-]\d{2}:?\d{2}))(.*)$/;
 
-// Locale-fixed dd.MM.yyyy HH:mm in the Europe/Berlin display zone — the
-// rest of the app shows timestamps in Berlin time (`format-locale.ts`),
-// so a token issued at 19:46 UTC must read as 21:46 in summer / 20:46
-// in winter, not the raw UTC clock.
-const TOKEN_NAME_DATE_FORMATTER = new Intl.DateTimeFormat("de-DE", {
-  timeZone: "Europe/Berlin",
-  day: "2-digit",
-  month: "2-digit",
-  year: "numeric",
-  hour: "2-digit",
-  minute: "2-digit",
-  hour12: false,
-});
-
-function formatTokenName(name: string): string {
+/**
+ * Issue #66 (date-format sweep) — this used to hard-code `de-DE` +
+ * `Europe/Berlin`, so a non-German admin saw a German-formatted
+ * timestamp baked into the token name regardless of their own locale
+ * or profile timezone. Routes through the same `fmt.dateTime` every
+ * other surface renders through, so the admin's locale, hour-cycle
+ * preference, and profile timezone all apply here too.
+ */
+function formatTokenName(name: string, fmt: Formatters): string {
   const match = TOKEN_NAME_ISO_RE.exec(name);
   if (!match) return name;
   const [, prefix, iso, rest] = match;
   const d = new Date(iso);
   if (Number.isNaN(d.getTime())) return name;
-  // Intl emits "05.05.2026, 21:46" — strip the comma so the suffix
-  // reads as a single date+time chunk.
-  const stamp = TOKEN_NAME_DATE_FORMATTER.format(d).replace(",", "");
+  // `fmt.dateTime` emits "05.05.2026, 21:46" — strip the comma so the
+  // suffix reads as a single date+time chunk.
+  const stamp = fmt.dateTime(d).replace(",", "");
   const formatted = `${prefix} · ${stamp}`;
   return rest && rest.trim() ? `${formatted} ${rest.trim()}` : formatted;
 }
 
 export function ApiTokenOverviewSection() {
   const { t } = useTranslations();
+  const fmt = useFormatters();
   // v1.4.19 phase A7 — `/admin/api-tokens` is a dedicated single-
   // section route. The previous pattern carried a "Collapse / Expand"
   // toggle as an escape hatch from the v1.4 shared admin page where
@@ -232,7 +228,9 @@ export function ApiTokenOverviewSection() {
                           <TruncatedCell value={token.user.username} />
                         </td>
                         <td className="max-w-0 px-3 py-2">
-                          <TruncatedCell value={formatTokenName(token.name)} />
+                          <TruncatedCell
+                            value={formatTokenName(token.name, fmt)}
+                          />
                         </td>
                         <td className="max-w-0 px-3 py-2">
                           <div className="flex flex-wrap gap-1">
@@ -303,7 +301,7 @@ export function ApiTokenOverviewSection() {
                         <div className="min-w-0 flex-1">
                           <div className="flex items-center gap-2">
                             <TruncatedCell
-                              value={formatTokenName(token.name)}
+                              value={formatTokenName(token.name, fmt)}
                               className="min-w-0 flex-1 font-medium"
                             />
                             <TokenStatusBadge token={token} size="xs" />

src/components/charts/health-chart.tsx

@@ -952,7 +952,7 @@ export function HealthChart({
       const allData: ChartDataPoint[] = Array.from(dailyAggregates.values())
         .map((bucket) => {
           const point: ChartDataPoint = {
-            date: tzFmt.dateShort(new Date(bucket.timestamp)),
+            date: tzFmt.dateShortSmart(new Date(bucket.timestamp)),
             timestamp: bucket.timestamp,
           };
 
@@ -1079,7 +1079,7 @@ export function HealthChart({
           ).points.map<ChartDataPoint>((point) => {
             const date = new Date(point.timestamp);
             const out: ChartDataPoint = {
-              date: tzFmt.dateShort(date),
+              date: tzFmt.dateShortSmart(date),
               timestamp: point.timestamp,
             };
             for (const [type, value] of Object.entries(point.values)) {
@@ -1209,7 +1209,7 @@ export function HealthChart({
     // Index shifted rows by the same day-key the chart already uses.
     const shiftedByDay = new Map<string, Record<string, number>>();
     for (const row of shifted) {
-      const dayKey = tzFmt.dateShort(new Date(row.timestamp));
+      const dayKey = tzFmt.dateShortSmart(new Date(row.timestamp));
       const slot = shiftedByDay.get(dayKey) ?? {};
       for (const [type, value] of Object.entries(row.values)) {
         if (typeof value === "number" && Number.isFinite(value)) {

src/components/charts/medication-compliance-chart.tsx

@@ -284,7 +284,7 @@ export function MedicationComplianceChart({
   const chartData = useMemo(
     () =>
       data
-        ? aggregateMedicationCompliance(data, (d) => tzFmt.dateShort(d))
+        ? aggregateMedicationCompliance(data, (d) => tzFmt.dateShortSmart(d))
         : [],
     [data, tzFmt],
   );

src/components/charts/mood-chart.tsx

@@ -400,7 +400,7 @@ export function MoodChart({
 
     const allPoints: ChartDataPoint[] = data.entries
       .map((entry) => ({
-        date: tzFmt.dateShort(new Date(dayKeyToTimestamp(entry.date))),
+        date: tzFmt.dateShortSmart(new Date(dayKeyToTimestamp(entry.date))),
         timestamp: dayKeyToTimestamp(entry.date),
         pointIndex: 0,
         score: entry.score,
@@ -436,7 +436,7 @@ export function MoodChart({
             })),
             { bucket: bucketType },
           ).points.map((point) => ({
-            date: tzFmt.dateShort(new Date(point.timestamp)),
+            date: tzFmt.dateShortSmart(new Date(point.timestamp)),
             timestamp: point.timestamp,
             pointIndex: 0,
             score: point.values.score,
@@ -513,7 +513,7 @@ export function MoodChart({
 
     const shiftedByDay = new Map<string, number>();
     for (const row of shifted) {
-      const dayKey = tzFmt.dateShort(new Date(row.timestamp));
+      const dayKey = tzFmt.dateShortSmart(new Date(row.timestamp));
       if (typeof row.score === "number" && Number.isFinite(row.score)) {
         shiftedByDay.set(dayKey, row.score);
       }

src/components/charts/nutrient-daily-bar-chart.tsx

@@ -14,7 +14,7 @@ import {
 
 import { CHART_HEIGHT_PX } from "@/lib/charts/constants";
 import { prefersReducedMotion } from "@/lib/charts/reduced-motion";
-import { formatDateShort } from "@/lib/format";
+import { useFormatters } from "@/lib/i18n/context";
 
 import { RichChartTooltip, type RichTooltipRow } from "./chart-tooltip";
 
@@ -49,6 +49,7 @@ export function NutrientDailyBarChart({
   valueLabel,
   referenceValue,
 }: NutrientDailyBarChartProps) {
+  const fmt = useFormatters();
   const points = useMemo(
     () => days.map((d) => ({ day: d.day, amount: Math.round(d.amount) })),
     [days],
@@ -77,7 +78,7 @@ export function NutrientDailyBarChart({
         />
         <XAxis
           dataKey="day"
-          tickFormatter={(day: string) => formatDateShort(dayToDate(day))}
+          tickFormatter={(day: string) => fmt.dateShortSmart(dayToDate(day))}
           tick={{ fontSize: 11, fill: "var(--muted-foreground)" }}
           stroke="var(--border)"
           minTickGap={24}
@@ -116,7 +117,7 @@ export function NutrientDailyBarChart({
             return (
               <RichChartTooltip
                 active
-                label={formatDateShort(dayToDate(point.day))}
+                label={fmt.dateShortSmart(dayToDate(point.day))}
                 rows={rows}
               />
             );

src/components/custom-metrics/custom-metric-chart.tsx

@@ -16,8 +16,7 @@ import {
 import { Button } from "@/components/ui/button";
 import { CHART_HEIGHT_PX } from "@/lib/charts/constants";
 import { prefersReducedMotion } from "@/lib/charts/reduced-motion";
-import { formatDateShort } from "@/lib/format";
-import { useTranslations } from "@/lib/i18n/context";
+import { useTranslations, useFormatters } from "@/lib/i18n/context";
 
 import { RichChartTooltip, type RichTooltipRow } from "../charts/chart-tooltip";
 import { formatMetricValue } from "./format-value";
@@ -62,6 +61,7 @@ export function CustomMetricChart({
   decimals: number | null;
 }) {
   const { t } = useTranslations();
+  const fmt = useFormatters();
   const [range, setRange] = useState<RangeKey>("365");
   const [nowMs] = useState(() => Date.now());
 
@@ -136,7 +136,7 @@ export function CustomMetricChart({
                 type="number"
                 scale="time"
                 domain={["dataMin", "dataMax"]}
-                tickFormatter={(ts: number) => formatDateShort(new Date(ts))}
+                tickFormatter={(ts: number) => fmt.dateShortSmart(new Date(ts))}
                 tick={{ fontSize: 11, fill: "var(--muted-foreground)" }}
                 stroke="var(--border)"
                 minTickGap={32}
@@ -192,7 +192,7 @@ export function CustomMetricChart({
                   return (
                     <RichChartTooltip
                       active
-                      label={formatDateShort(new Date(point.timestamp))}
+                      label={fmt.dateShortSmart(new Date(point.timestamp))}
                       rows={rows}
                     />
                   );

src/components/cycle/bbt-chart.tsx

@@ -191,7 +191,9 @@ export function BbtChart({
                     scale="time"
                     domain={["dataMin", "dataMax"]}
                     ticks={ticks}
-                    tickFormatter={(v) => fmt.dateShort(new Date(v as number))}
+                    tickFormatter={(v) =>
+                      fmt.dateShortSmart(new Date(v as number))
+                    }
                     tick={{ fontSize: 11, fill: "var(--muted-foreground)" }}
                     tickLine={false}
                     axisLine={false}
@@ -285,7 +287,9 @@ function BbtTooltip(props: {
         "bg-popover border-border rounded-md border px-2.5 py-2 text-xs shadow-md",
       )}
     >
-      <p className="text-muted-foreground">{fmt.dateShort(new Date(p.t))}</p>
+      <p className="text-muted-foreground">
+        {fmt.dateShortSmart(new Date(p.t))}
+      </p>
       <p className="text-foreground font-medium tabular-nums">
         {t("cycle.bbt.tooltipTemp", { temp: fmt.number(p.temp) })}
       </p>

src/components/cycle/predictions-panel.tsx

@@ -11,7 +11,8 @@ import {
 } from "@/components/ui/card";
 import { Badge } from "@/components/ui/badge";
 import { TileHeader } from "@/components/insights/tile-header";
-import { useTranslations } from "@/lib/i18n/context";
+import { useTranslations, useFormatters } from "@/lib/i18n/context";
+import type { Formatters } from "@/lib/format-locale";
 import { FERTILE_HUE, FLOW_HUE, OVULATION_HUE } from "./phase-tokens";
 import type { CyclePrediction, CycleHistoryResponse } from "./types";
 
@@ -26,12 +27,17 @@ import type { CyclePrediction, CycleHistoryResponse } from "./types";
  * cycle-tracking on-ramp, not repeated beneath every prediction surface.
  */
 
-function formatDate(d: string): string {
+/**
+ * Issue #66 — was a bespoke `toLocaleDateString(undefined, …)` (browser
+ * locale, never the app's) with no year. Predictions run 1-2 cycles out, so
+ * a window straddling New Year's would otherwise print an unadorned "Jan 3"
+ * in December. Routes through the app-locale conditional-year formatter
+ * instead; `dateShortSmart` already renders day+month in the locale's field
+ * order and only adds the year when it differs from the current one.
+ */
+function formatDate(d: string, fmt: Formatters): string {
   // Render at noon UTC so the YYYY-MM-DD never rolls a day across tz.
-  return new Date(`${d}T12:00:00Z`).toLocaleDateString(undefined, {
-    month: "short",
-    day: "numeric",
-  });
+  return fmt.dateShortSmart(`${d}T12:00:00Z`);
 }
 
 function confidenceTone(c: number): {
@@ -60,6 +66,7 @@ export function PredictionsPanel({
   history,
 }: PredictionsPanelProps) {
   const { t } = useTranslations();
+  const fmt = useFormatters();
 
   return (
     <div className="space-y-4">
@@ -92,8 +99,9 @@ export function PredictionsPanel({
                 <Row
                   hue={FERTILE_HUE}
                   label={t("cycle.predictions.fertileWindow")}
-                  value={`${formatDate(prediction.fertileWindowStart)} – ${formatDate(
+                  value={`${formatDate(prediction.fertileWindowStart, fmt)} – ${formatDate(
                     prediction.fertileWindowEnd,
+                    fmt,
                   )}`}
                 />
               ) : null}
@@ -105,7 +113,7 @@ export function PredictionsPanel({
                       ? t("cycle.predictions.ovulationConfirmed")
                       : t("cycle.predictions.ovulation")
                   }
-                  value={formatDate(prediction.predictedOvulation)}
+                  value={formatDate(prediction.predictedOvulation, fmt)}
                 />
               ) : null}
             </>
@@ -120,6 +128,7 @@ export function PredictionsPanel({
 
 function NextPeriod({ prediction }: { prediction: CyclePrediction }) {
   const { t } = useTranslations();
+  const fmt = useFormatters();
   const tone = confidenceTone(prediction.confidence);
   return (
     <div className="space-y-1.5">
@@ -128,8 +137,8 @@ function NextPeriod({ prediction }: { prediction: CyclePrediction }) {
           hue={FLOW_HUE}
           label={t("cycle.predictions.nextPeriod")}
           value={t("cycle.predictions.nextPeriodWindow", {
-            low: formatDate(prediction.nextPeriodStartLow),
-            high: formatDate(prediction.nextPeriodStartHigh),
+            low: formatDate(prediction.nextPeriodStartLow, fmt),
+            high: formatDate(prediction.nextPeriodStartHigh, fmt),
           })}
         />
         <Badge variant={tone.variant} className="shrink-0">
@@ -186,6 +195,7 @@ function HistoryCard({
   history: CycleHistoryResponse | undefined;
 }) {
   const { t } = useTranslations();
+  const fmt = useFormatters();
   const stats = history?.stats;
   // Most-recent observed cycles (the spread the regularity number summarises —
   // seeing it builds trust; the data was already on the wire). QA H2.
@@ -253,10 +263,10 @@ function HistoryCard({
                     className="flex items-center justify-between gap-3 py-2 text-sm"
                   >
                     <span className="text-foreground tabular-nums">
-                      {formatDate(c.startDate)}
+                      {formatDate(c.startDate, fmt)}
                       {" – "}
                       {c.endDate
-                        ? formatDate(c.endDate)
+                        ? formatDate(c.endDate, fmt)
                         : t("cycle.history.ongoing")}
                     </span>
                     <span className="text-muted-foreground flex items-center gap-2 tabular-nums">

src/components/illness/illness-day-timeline.tsx

@@ -34,7 +34,7 @@ function DayLogRow({ log }: { log: IllnessDayLogDTO }) {
   return (
     <div className="border-border/60 space-y-2 border-l-2 pl-3">
       <p className="text-muted-foreground text-xs font-medium tracking-wide uppercase">
-        {fmt.dateShort(`${log.date}T12:00:00`)}
+        {fmt.dateShortSmart(`${log.date}T12:00:00`)}
       </p>
 
       {log.symptoms.length > 0 ? (

src/components/illness/illness-episode-detail.tsx

@@ -82,11 +82,11 @@ export function IllnessEpisodeDetail({ episodeId }: { episodeId: string }) {
               </Badge>
               <span className="text-muted-foreground text-xs">
                 {t("illness.onsetOn", {
-                  date: fmt.dateShort(new Date(episode.onsetAt)),
+                  date: fmt.dateShortSmart(new Date(episode.onsetAt)),
                 })}
                 {episode.resolvedAt
                   ? ` · ${t("illness.recoveredOn", {
-                      date: fmt.dateShort(new Date(episode.resolvedAt)),
+                      date: fmt.dateShortSmart(new Date(episode.resolvedAt)),
                     })}`
                   : ""}
               </span>

src/components/illness/illness-settings.tsx

@@ -43,7 +43,7 @@ export function IllnessSettings() {
         : e.lifecycle === "CHRONIC_ONGOING"
           ? t("illness.status.ongoing")
           : t("illness.status.active")
-    } · ${fmt.dateShort(new Date(e.onsetAt))}`,
+    } · ${fmt.dateShortSmart(new Date(e.onsetAt))}`,
   }));
 
   return (

src/components/illness/illness-view.tsx

@@ -103,7 +103,7 @@ function EpisodeCard({
                   : t("illness.status.recovered")}
               </Badge>
               <span className="text-muted-foreground">
-                {fmt.dateShort(new Date(episode.onsetAt))}
+                {fmt.dateShortSmart(new Date(episode.onsetAt))}
               </span>
             </div>
           </div>
@@ -167,11 +167,11 @@ function EpisodeCard({
 
         <p className="text-muted-foreground text-xs">
           {t("illness.onsetOn", {
-            date: fmt.dateShort(new Date(episode.onsetAt)),
+            date: fmt.dateShortSmart(new Date(episode.onsetAt)),
           })}
           {episode.resolvedAt
             ? ` · ${t("illness.recoveredOn", {
-                date: fmt.dateShort(new Date(episode.resolvedAt)),
+                date: fmt.dateShortSmart(new Date(episode.resolvedAt)),
               })}`
             : ""}
         </p>
@@ -192,7 +192,7 @@ function EpisodeCard({
                   >
                     <span className="truncate">{flare.label}</span>
                     <span className="text-muted-foreground shrink-0">
-                      {fmt.dateShort(new Date(flare.onsetAt))}
+                      {fmt.dateShortSmart(new Date(flare.onsetAt))}
                     </span>
                   </Link>
                 </li>

src/components/insights/intraday-pulse-chart.tsx

@@ -175,7 +175,7 @@ export function IntradayPulseChart({
 
   const dayLabel = isToday
     ? t("insights.intradayPulse.today")
-    : fmt.dateShort(new Date(`${dateKey}T12:00:00.000Z`));
+    : fmt.dateShortSmart(new Date(`${dateKey}T12:00:00.000Z`));
 
   return (
     <div

src/components/labs/lab-biomarker-chart.tsx

@@ -16,9 +16,8 @@ import {
 import { Button } from "@/components/ui/button";
 import { CHART_HEIGHT_PX } from "@/lib/charts/constants";
 import { prefersReducedMotion } from "@/lib/charts/reduced-motion";
-import { formatDateShort } from "@/lib/format";
 import { formatLabValue } from "@/lib/labs/format-value";
-import { useTranslations } from "@/lib/i18n/context";
+import { useTranslations, useFormatters } from "@/lib/i18n/context";
 
 import { RichChartTooltip, type RichTooltipRow } from "../charts/chart-tooltip";
 import type { LabResultDto } from "./types";
@@ -62,6 +61,7 @@ export function LabBiomarkerChart({
   upperBound: number | null;
 }) {
   const { t } = useTranslations();
+  const fmt = useFormatters();
   const [range, setRange] = useState<RangeKey>("365");
   // Capture "now" once at mount so the recency filter stays pure across
   // re-renders (an inline `Date.now()` in render is impure).
@@ -145,7 +145,7 @@ export function LabBiomarkerChart({
                 type="number"
                 scale="time"
                 domain={["dataMin", "dataMax"]}
-                tickFormatter={(ts: number) => formatDateShort(new Date(ts))}
+                tickFormatter={(ts: number) => fmt.dateShortSmart(new Date(ts))}
                 tick={{ fontSize: 11, fill: "var(--muted-foreground)" }}
                 stroke="var(--border)"
                 minTickGap={32}
@@ -204,7 +204,7 @@ export function LabBiomarkerChart({
                   return (
                     <RichChartTooltip
                       active
-                      label={formatDateShort(new Date(point.timestamp))}
+                      label={fmt.dateShortSmart(new Date(point.timestamp))}
                       rows={rows}
                     />
                   );

src/components/medications/dose-history-ledger.tsx

@@ -82,7 +82,7 @@ import {
   useFormatters,
   useDateFormatPreference,
 } from "@/lib/i18n/context";
-import { formatDateWithWeekday } from "@/lib/date-format";
+import { formatDateWithWeekdaySmart } from "@/lib/date-format";
 import {
   invalidateKeys,
   medicationDependentKeys,
@@ -448,7 +448,7 @@ export function DoseHistoryLedger({
                   the DEVICE zone and could shift the heading a day when
                   browser ≠ profile zone; the day-key label renders
                   UTC-pinned instead (zone-independent, weekday included). */}
-              {formatDateWithWeekday(group.dayKey, dateFormatPref, locale)}
+              {formatDateWithWeekdaySmart(group.dayKey, dateFormatPref, locale)}
             </h3>
             <ul className="border-border/60 divide-border/60 divide-y rounded-md border">
               {group.rows.map((row, i) => (

src/components/medications/dose-strength-curve.tsx

@@ -218,7 +218,7 @@ export function DoseStrengthCurve({
             scale="time"
             domain={["dataMin", "dataMax"]}
             ticks={ticks}
-            tickFormatter={(v) => fmt.dateShort(new Date(v as number))}
+            tickFormatter={(v) => fmt.dateShortSmart(new Date(v as number))}
             tick={{ fontSize: 11, fill: "var(--muted-foreground)" }}
             tickLine={false}
             axisLine={false}
@@ -237,7 +237,7 @@ export function DoseStrengthCurve({
               strokeOpacity: 0.3,
               strokeDasharray: "3 3",
             }}
-            labelFormatter={(v) => fmt.dateShort(new Date(v as number))}
+            labelFormatter={(v) => fmt.dateShortSmart(new Date(v as number))}
             formatter={(value) => [
               `${fmt.number(value as number)} ${unit}`,
               t("medications.doseStrength.tooltipLabel"),

src/components/medications/glp1-medication-card.tsx

@@ -420,7 +420,7 @@ export function Glp1MedicationCard({
     if (next.daysAway === 0) return t("medications.glp1NextInjectionToday");
     if (next.daysAway === 1) return t("medications.glp1NextInjectionTomorrow");
     const dayName = weekdayLabel(getDayOfWeekInTz(next.date, displayTz));
-    const dateShort = fmt.dateShort(next.date);
+    const dateShort = fmt.dateShortSmart(next.date);
     return t("medications.glp1NextInjectionDays", {
       label: `${dayName}, ${dateShort}`,
       days: next.daysAway,
@@ -469,7 +469,7 @@ export function Glp1MedicationCard({
     medication.nextDueOverdue && next
       ? diffDays(next.date, now) === 0
         ? formatTime(next.date.toISOString())
-        : `${weekdayLabel(getDayOfWeekInTz(next.date, displayTz))}, ${fmt.dateShort(next.date)}`
+        : `${weekdayLabel(getDayOfWeekInTz(next.date, displayTz))}, ${fmt.dateShortSmart(next.date)}`
       : null;
 
   const nextLine =

src/components/medications/medication-card.tsx

@@ -437,7 +437,7 @@ export function MedicationCard({
             } else if (diffDays <= 5) {
               dayLabel = weekdayLabel(nextDate.getDay());
             } else {
-              dayLabel = fmt.dateWithWeekday(nextDate);
+              dayLabel = fmt.dateWithWeekdaySmart(nextDate);
             }
           }
 

src/components/medications/medication-table.tsx

@@ -551,7 +551,7 @@ function MedicationTableRowItem({
             ? t("medications.tomorrow")
             : diffDays <= 5
               ? weekdayLabel(nextDate.getDay())
-              : fmt.dateWithWeekday(nextDate);
+              : fmt.dateWithWeekdaySmart(nextDate);
       nextCell = (
         <span>
           {dayLabel}, {formatTime(new Date(nextAt).toISOString())}

src/components/medications/side-effects-section.tsx

@@ -324,7 +324,7 @@ export function SideEffectsSection({ medicationId }: SideEffectsSectionProps) {
                       className="text-muted-foreground w-14 shrink-0 text-right text-xs tabular-nums"
                       data-slot="side-effect-row-date"
                     >
-                      {fmt.dateShort(new Date(row.occurredAt))}
+                      {fmt.dateShortSmart(new Date(row.occurredAt))}
                     </p>
                   </div>
                   {row.notes && (

src/components/medications/titration-timeline.tsx

@@ -221,9 +221,11 @@ export function TitrationTimeline({
                     </p>
                     <p className="text-muted-foreground shrink-0 text-xs">
                       {step.isPast
-                        ? fmt.dateShort(new Date(step.effectiveFrom))
+                        ? fmt.dateShortSmart(new Date(step.effectiveFrom))
                         : t("medications.titration.plannedFor", {
-                            date: fmt.dateShort(new Date(step.effectiveFrom)),
+                            date: fmt.dateShortSmart(
+                              new Date(step.effectiveFrom),
+                            ),
                           })}
                     </p>
                   </div>

src/components/mental-health/assessment-history-chart.tsx

@@ -34,8 +34,7 @@ import {
 import { RichChartTooltip, type RichTooltipRow } from "../charts/chart-tooltip";
 import { CHART_HEIGHT_PX } from "@/lib/charts/constants";
 import { prefersReducedMotion } from "@/lib/charts/reduced-motion";
-import { formatDateShort } from "@/lib/format";
-import { useTranslations } from "@/lib/i18n/context";
+import { useTranslations, useFormatters } from "@/lib/i18n/context";
 import { INSTRUMENTS } from "@/lib/mental-health/instruments";
 
 import type { AssessmentRow, InstrumentId } from "./types";
@@ -55,6 +54,7 @@ export function AssessmentHistoryChart({
   rows: AssessmentRow[];
 }) {
   const { t } = useTranslations();
+  const fmt = useFormatters();
   const def = INSTRUMENTS[instrument];
 
   const points = useMemo<ChartPoint[]>(() => {
@@ -103,7 +103,7 @@ export function AssessmentHistoryChart({
           type="number"
           scale="time"
           domain={["dataMin", "dataMax"]}
-          tickFormatter={(ts: number) => formatDateShort(new Date(ts))}
+          tickFormatter={(ts: number) => fmt.dateShortSmart(new Date(ts))}
           tick={{ fontSize: 11, fill: "var(--muted-foreground)" }}
           stroke="var(--border)"
           minTickGap={32}
@@ -139,7 +139,7 @@ export function AssessmentHistoryChart({
             return (
               <RichChartTooltip
                 active
-                label={formatDateShort(new Date(point.timestamp))}
+                label={fmt.dateShortSmart(new Date(point.timestamp))}
                 rows={rowsOut}
               />
             );

src/components/settings/trusted-devices-card.tsx

@@ -15,7 +15,7 @@ import { Loader2, ShieldCheck } from "lucide-react";
 import { Button } from "@/components/ui/button";
 import { SettingsCard } from "@/components/settings/settings-card";
 import { SettingsCardHeader } from "@/components/settings/_card-header";
-import { useTranslations } from "@/lib/i18n/context";
+import { useTranslations, useFormatters } from "@/lib/i18n/context";
 import { queryKeys } from "@/lib/query-keys";
 import { apiGet, apiDelete } from "@/lib/api/api-fetch";
 
@@ -34,6 +34,7 @@ export function TrustedDevicesCard({
   isAuthenticated: boolean;
 }) {
   const { t } = useTranslations();
+  const fmt = useFormatters();
   const queryClient = useQueryClient();
   const [status, setStatus] = useState<string | null>(null);
 
@@ -125,7 +126,7 @@ export function TrustedDevicesCard({
                   </p>
                   <p className="text-muted-foreground text-xs">
                     {t("settings.security.trustedDevices.expires", {
-                      date: new Date(d.expiresAt).toLocaleDateString(),
+                      date: fmt.date(d.expiresAt),
                     })}
                   </p>
                 </div>

src/components/ui/filter-bar.tsx

@@ -229,7 +229,7 @@ export function FilterBarDateRange({
   const fmt = useFormatters();
   const active = from !== "" || to !== "";
   const display = active
-    ? `${from ? fmt.dateShort(from) : "…"} – ${to ? fmt.dateShort(to) : "…"}`
+    ? `${from ? fmt.dateShortSmart(from) : "…"} – ${to ? fmt.dateShortSmart(to) : "…"}`
     : null;
   const clear = () => {
     onFromChange("");

src/lib/__tests__/date-format.test.ts

@@ -5,11 +5,12 @@
  * field order the `<DateField>` primitive and `useFormatters().date()` render.
  * AUTO defers to the active locale; DMY / MDY / YMD pin the order regardless.
  */
-import { describe, expect, it } from "vitest";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 
 import {
   formatDate,
   formatDateWithWeekday,
+  formatDateWithWeekdaySmart,
   parseIsoDate,
   resolveDateLocale,
   isDateFormatPreference,
@@ -112,6 +113,41 @@ describe("formatDateWithWeekday (#490)", () => {
   });
 });
 
+// Issue #66 (date-format sweep) — the dose-history ledger scrolls day
+// groups across year boundaries; a bare "Di., 16.12." from last December
+// must not read as this year's. "Now" is faked so the boundary is
+// deterministic regardless of the day this suite runs.
+describe("formatDateWithWeekdaySmart (#66)", () => {
+  beforeEach(() => {
+    vi.useFakeTimers();
+    vi.setSystemTime(new Date("2026-07-10T12:00:00Z"));
+  });
+
+  afterEach(() => {
+    vi.useRealTimers();
+  });
+
+  it("omits the year for a day key in the current UTC year", () => {
+    expect(formatDateWithWeekdaySmart("2026-07-14", "AUTO", "en")).toBe(
+      "Tue, 07/14",
+    );
+  });
+
+  it("adds the year for a day key from a prior UTC year", () => {
+    expect(formatDateWithWeekdaySmart("2025-12-16", "AUTO", "en")).toBe(
+      "Tue, 12/16/2025",
+    );
+    expect(formatDateWithWeekdaySmart("2025-12-16", "AUTO", "de")).toBe(
+      "Di., 16.12.2025",
+    );
+  });
+
+  it("returns an empty string for empty / unparseable input", () => {
+    expect(formatDateWithWeekdaySmart("", "AUTO", "en")).toBe("");
+    expect(formatDateWithWeekdaySmart(null, "AUTO", "en")).toBe("");
+  });
+});
+
 describe("parseIsoDate", () => {
   it("parses a valid ISO calendar date to a UTC midnight Date", () => {
     const d = parseIsoDate("2026-02-19");

src/lib/__tests__/format-locale.test.ts

@@ -265,17 +265,6 @@ describe("makeFormatters", () => {
       // that prints as 2025 in New York must carry the year.
       expect(nyFmt.dateShortSmart(newYearUtcEve)).toContain("2025");
     });
-
-    it("monthYear always carries the year (chart axis / next-dose labels)", () => {
-      const de = makeFormatters("de");
-      const en = makeFormatters("en");
-      const dec = new Date("2025-12-30T10:00:00Z");
-      const jan = new Date("2026-01-15T10:00:00Z");
-      expect(de.monthYear(dec)).toContain("2025");
-      expect(de.monthYear(jan)).toContain("2026");
-      expect(en.monthYear(dec)).toBe("Dec 2025");
-      expect(en.monthYear(jan)).toBe("Jan 2026");
-    });
   });
 });
 

src/lib/date-format.ts

@@ -167,6 +167,31 @@ export function formatDateWithWeekday(
   });
 }
 
+/**
+ * Same field set as {@link formatDateWithWeekday}, but adds the year
+ * whenever `value`'s UTC calendar year differs from the current UTC year
+ * — issue #66 (date-format sweep). A day group from a previous year (e.g.
+ * the dose-history ledger scrolled past a year boundary) must not read as
+ * this year's "Di., 16.12.".
+ */
+export function formatDateWithWeekdaySmart(
+  value: Date | string | null | undefined,
+  pref: DateFormatPreference,
+  locale: Locale,
+): string {
+  if (value === null || value === undefined || value === "") return "";
+  const date = value instanceof Date ? value : parseIsoDate(value);
+  if (date === null || Number.isNaN(date.getTime())) return "";
+  const showYear = date.getUTCFullYear() !== new Date().getUTCFullYear();
+  return date.toLocaleDateString(resolveDateLocale(pref, locale), {
+    timeZone: "UTC",
+    weekday: "short",
+    day: "2-digit",
+    month: "2-digit",
+    ...(showYear ? { year: "numeric" as const } : {}),
+  });
+}
+
 /**
  * Parse a `yyyy-MM-dd` string to a UTC `Date` at midnight. Returns null on
  * a value that is not exactly the ISO calendar-date shape so callers can

src/lib/format-locale.ts

@@ -171,11 +171,6 @@ export interface Formatters {
   dateWithWeekdaySmart: (value: DateInput) => string;
   /** For axis labels: 3-letter month abbreviation. */
   monthShort: (value: DateInput) => string;
-  /**
-   * Month + year, e.g. "Feb. 2026" / "Feb 2026" — for axis labels and
-   * next-dose captions that need to disambiguate a Dec → Jan rollover.
-   */
-  monthYear: (value: DateInput) => string;
 }
 
 export function makeFormatters(
@@ -299,13 +294,6 @@ export function makeFormatters(
         timeZone: tz,
         month: "short",
       }).format(asDate(value)),
-
-    monthYear: (value) =>
-      getDateTimeFormat(intlLocale, {
-        timeZone: tz,
-        month: "short",
-        year: "numeric",
-      }).format(asDate(value)),
   };
 }