diff --git a/frontend/src/views/personal/CalendarView.vue b/frontend/src/views/personal/CalendarView.vue
index 6300508..3200ac7 100644
--- a/frontend/src/views/personal/CalendarView.vue
+++ b/frontend/src/views/personal/CalendarView.vue
@@ -467,6 +467,8 @@ export default {
             const newDate = new Date(this.currentDate);
             switch (this.currentView) {
                 case 'month':
+                    // Set day to 1 first to avoid month overflow (e.g., Jan 31 - 1 month = Dec 31, not Dec 1)
+                    newDate.setDate(1);
                     newDate.setMonth(newDate.getMonth() - 1);
                     break;
                 case 'week':
@@ -483,6 +485,8 @@ export default {
             const newDate = new Date(this.currentDate);
             switch (this.currentView) {
                 case 'month':
+                    // Set day to 1 first to avoid month overflow (e.g., Jan 30 + 1 month would skip Feb)
+                    newDate.setDate(1);
                     newDate.setMonth(newDate.getMonth() + 1);
                     break;
                 case 'week':