diff --git a/src/pages/Calendar.jsx b/src/pages/Calendar.jsx
index 4f5e436..dbf92f5 100644
--- a/src/pages/Calendar.jsx
+++ b/src/pages/Calendar.jsx
@@ -111,10 +111,10 @@ export default function Calendar() {
   }, [currentDate]);
 
   const eventsForDay = (day) => {
-    const dayStr = day.toISOString().split('T')[0];
+    const dayStr = toLocalDateStr(day);
     return events.filter(ev => {
-      const start = ev.start_time.split('T')[0];
-      const end = ev.end_time.split('T')[0];
+      const start = toLocalDateStr(new Date(ev.start_time));
+      const end = toLocalDateStr(new Date(ev.end_time));
       return dayStr >= start && dayStr <= end;
     });
   };
@@ -826,6 +826,13 @@ export default function Calendar() {
 }
 
 // Helpers
+function toLocalDateStr(date) {
+  const y = date.getFullYear();
+  const m = String(date.getMonth() + 1).padStart(2, '0');
+  const d = String(date.getDate()).padStart(2, '0');
+  return `${y}-${m}-${d}`;
+}
+
 function toLocalDateTimeStr(date) {
   const y = date.getFullYear();
   const m = String(date.getMonth() + 1).padStart(2, '0');