diff --git a/client/src/components/Dawarich/dawarichSuggestionModel.ts b/client/src/components/Dawarich/dawarichSuggestionModel.ts
index 7dbfe2179..0e7927e31 100644
--- a/client/src/components/Dawarich/dawarichSuggestionModel.ts
+++ b/client/src/components/Dawarich/dawarichSuggestionModel.ts
@@ -34,7 +34,9 @@ export function groupByDay(suggestions: DawarichSuggestion[]): SuggestionDay[] {
     else byDate.set(stay.localDate, [stay])
   }
 
-  const oldestFirst = [...byDate.keys()].sort()
+  // ISO dates, so lexicographic order IS chronological order. Spelled out rather than
+  // left bare, and deliberately not locale-aware, which would vary by runtime.
+  const oldestFirst = [...byDate.keys()].sort((a, b) => (a < b ? -1 : a > b ? 1 : 0))
   return oldestFirst
     .map((date, index) => ({
       date,
diff --git a/client/src/components/Map/dawarichTrail.ts b/client/src/components/Map/dawarichTrail.ts
index 97adec6af..5fc536d6a 100644
--- a/client/src/components/Map/dawarichTrail.ts
+++ b/client/src/components/Map/dawarichTrail.ts
@@ -130,7 +130,9 @@ export function collapsedDayDates(
     const foldedInPlan = !!expandedDayIds && !expandedDayIds.has(day.id)
     if (foldedInPlan || collapsedDayIds?.has(day.id)) dates.add(day.date)
   }
-  return [...dates].sort()
+  // Explicit rather than bare: these are ISO dates, where lexicographic IS chronological,
+  // and a locale-aware comparison would reorder them differently per runtime.
+  return [...dates].sort((a, b) => (a < b ? -1 : a > b ? 1 : 0))
 }
 
 /** The overlay as a GeoJSON FeatureCollection, for the GL renderer. */
diff --git a/client/src/hooks/useDawarichJournalTrail.ts b/client/src/hooks/useDawarichJournalTrail.ts
index de9e7c380..a16068c24 100644
--- a/client/src/hooks/useDawarichJournalTrail.ts
+++ b/client/src/hooks/useDawarichJournalTrail.ts
@@ -37,7 +37,9 @@ export function useDawarichJournalTrail(
   // here rather than trusting insertion order.
   const window = useMemo(() => {
     if (dates.size === 0) return null
-    const sorted = [...dates].sort()
+    // ISO dates: lexicographic order is chronological, and staying locale-independent
+    // keeps the window identical on every runtime.
+    const sorted = [...dates].sort((a, b) => (a < b ? -1 : a > b ? 1 : 0))
     return { from: `${sorted[0]}T00:00:00Z`, to: `${sorted[sorted.length - 1]}T23:59:59Z` }
   }, [dates])
 
diff --git a/server/src/nest/integrations/dawarich.helpers.ts b/server/src/nest/integrations/dawarich.helpers.ts
index 428666290..e82e28aaa 100644
--- a/server/src/nest/integrations/dawarich.helpers.ts
+++ b/server/src/nest/integrations/dawarich.helpers.ts
@@ -340,7 +340,8 @@ export function bucketPointsByDay(
     else byDay.set(date, [{ lat, lng, ts }]);
   }
 
-  const dates = [...byDay.keys()].sort();
+  // ISO dates, so lexicographic order is chronological. Explicit and locale-independent.
+  const dates = [...byDay.keys()].sort((a, b) => (a < b ? -1 : a > b ? 1 : 0));
   const days: DawarichTrackDay[] = [];
 
   for (let d = 0; d < dates.length; d++) {
diff --git a/server/src/nest/maps/providers/amap.provider.ts b/server/src/nest/maps/providers/amap.provider.ts
index 83dca9f13..e273cf81c 100644
--- a/server/src/nest/maps/providers/amap.provider.ts
+++ b/server/src/nest/maps/providers/amap.provider.ts
@@ -203,7 +203,10 @@ export class AmapPlacesProvider implements PlacesProvider {
     if (!secret) return null;
     const signed = { ...params, key: this.credential.key, output: 'JSON' };
     const canonical = Object.keys(signed)
-      .sort()
+      // Byte order, and it has to stay byte order: Amap computes the same signature over
+      // the same sorted names, so a locale-aware comparison would produce a signature the
+      // other side rejects.
+      .sort((a, b) => (a < b ? -1 : a > b ? 1 : 0))
       .map((k) => `${k}=${signed[k]}`)
       .join('&');
     return createHash('md5').update(`${canonical}${secret}`).digest('hex');