diff --git a/frontend/src/components/EventSlideOver.vue b/frontend/src/components/EventSlideOver.vue
index 5c5a776..0eb2c39 100644
--- a/frontend/src/components/EventSlideOver.vue
+++ b/frontend/src/components/EventSlideOver.vue
@@ -68,9 +68,11 @@ function resetForm() {
   if (props.event) {
     title.value = props.event.title;
     allDay.value = props.event.all_day;
-    startDate.value = dateFromIso(props.event.start_dt);
+    // All-day events: use UTC date string directly to avoid timezone shifting
+    // (UTC midnight parsed through new Date() becomes the previous day in UTC-X zones)
+    startDate.value = props.event.all_day ? props.event.start_dt.slice(0, 10) : dateFromIso(props.event.start_dt);
     startTime.value = props.event.all_day ? "" : timeFromIso(props.event.start_dt);
-    endDate.value = props.event.end_dt ? dateFromIso(props.event.end_dt) : "";
+    endDate.value = props.event.end_dt ? (props.event.all_day ? props.event.end_dt.slice(0, 10) : dateFromIso(props.event.end_dt)) : "";
     endTime.value = props.event.end_dt && !props.event.all_day ? timeFromIso(props.event.end_dt) : "";
     description.value = props.event.description || "";
     location.value = props.event.location || "";
diff --git a/frontend/src/views/CalendarView.vue b/frontend/src/views/CalendarView.vue
index a6ac12e..590ac3f 100644
--- a/frontend/src/views/CalendarView.vue
+++ b/frontend/src/views/CalendarView.vue
@@ -39,11 +39,13 @@ function closeSlideOver() {
 const eventCache = new Map<number, EventEntry>();
 
 function toFcEvent(e: EventEntry) {
+  // For all-day events pass date-only strings so FullCalendar never shifts
+  // the date through timezone conversion (UTC midnight → previous day in UTC-X).
   return {
     id: String(e.id),
     title: e.title,
-    start: e.start_dt,
-    end: e.end_dt ?? undefined,
+    start: e.all_day ? e.start_dt.slice(0, 10) : e.start_dt,
+    end: e.all_day ? (e.end_dt?.slice(0, 10) ?? undefined) : (e.end_dt ?? undefined),
     allDay: e.all_day,
     backgroundColor: e.color || undefined,
     borderColor: e.color || undefined,