diff --git a/frontend/src/pages/Calendar.tsx b/frontend/src/pages/Calendar.tsx
index 2a0a04d..0f03f19 100644
--- a/frontend/src/pages/Calendar.tsx
+++ b/frontend/src/pages/Calendar.tsx
@@ -44,15 +44,20 @@ const PRIORITY_DOT: Record<string, string> = {
 
 const WEEKDAYS = ['日', '一', '二', '三', '四', '五', '六']
 
+/** 本地日期格式化为 YYYY-MM-DD，避免 toISOString() 的 UTC 时区偏移 */
+const fmtDate = (d: Date) => `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, '0')}-${String(d.getDate()).padStart(2, '0')}`
+/** 本地月份格式化为 YYYY-MM */
+const fmtMonth = (d: Date) => `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, '0')}`
+
 export default function Calendar() {
   const queryClient = useQueryClient()
-  const [calendarMonth, setCalendarMonth] = useState(new Date().toISOString().slice(0, 7))
+  const [calendarMonth, setCalendarMonth] = useState(`${new Date().getFullYear()}-${String(new Date().getMonth() + 1).padStart(2, '0')}`)
   const [showEventForm, setShowEventForm] = useState(false)
   const [selectedDate, setSelectedDate] = useState<string | null>(null)
   const [typeFilter, setTypeFilter] = useState<string | null>(null)
   const [eventForm, setEventForm] = useState({
     title: '',
-    date: new Date().toISOString().slice(0, 10),
+    date: `${new Date().getFullYear()}-${String(new Date().getMonth() + 1).padStart(2, '0')}-${String(new Date().getDate()).padStart(2, '0')}`,
     type: 'CUSTOM',
     priority: 'medium',
     location: '',
@@ -81,7 +86,7 @@ export default function Calendar() {
       queryClient.invalidateQueries({ queryKey: ['custom-events'] })
       queryClient.invalidateQueries({ queryKey: ['calendar'] })
       setShowEventForm(false)
-      setEventForm({ title: '', date: selectedDate || new Date().toISOString().slice(0, 10), type: 'CUSTOM', priority: 'medium', location: '', description: '' })
+      setEventForm({ title: '', date: selectedDate || fmtDate(new Date()), type: 'CUSTOM', priority: 'medium', location: '', description: '' })
       toast.success('事件已创建')
     },
     onError: () => toast.error('创建事件失败'),
@@ -102,7 +107,7 @@ export default function Calendar() {
     const lastDay = new Date(year, mon, 0)
     const startWeekday = firstDay.getDay()
     const daysInMonth = lastDay.getDate()
-    const todayStr = new Date().toISOString().slice(0, 10)
+    const todayStr = fmtDate(new Date())
     const cells: Array<{ day: number | null; date: string | null; events: any[]; isToday: boolean }> = []
     for (let i = 0; i < startWeekday; i++) cells.push({ day: null, date: null, events: [], isToday: false })
     for (let d = 1; d <= daysInMonth; d++) {
@@ -131,14 +136,14 @@ export default function Calendar() {
   const prevMonth = () => {
     const [y, m] = calendarMonth.split('-').map(Number)
     const d = new Date(y, m - 2, 1)
-    setCalendarMonth(d.toISOString().slice(0, 7))
+    setCalendarMonth(fmtMonth(d))
   }
   const nextMonth = () => {
     const [y, m] = calendarMonth.split('-').map(Number)
     const d = new Date(y, m, 1)
-    setCalendarMonth(d.toISOString().slice(0, 7))
+    setCalendarMonth(fmtMonth(d))
   }
-  const goToday = () => setCalendarMonth(new Date().toISOString().slice(0, 7))
+  const goToday = () => setCalendarMonth(fmtMonth(new Date()))
 
   const handleDayClick = (date: string | null) => {
     if (!date) return
@@ -183,7 +188,7 @@ export default function Calendar() {
             <ChevronRight className="w-4 h-4" />
           </Button>
           <Button variant="secondary" size="sm" onClick={goToday}>今天</Button>
-          <Button size="sm" onClick={() => { setEventForm({ ...eventForm, date: new Date().toISOString().slice(0, 10) }); setShowEventForm(true) }}>
+          <Button size="sm" onClick={() => { setEventForm({ ...eventForm, date: fmtDate(new Date()) }); setShowEventForm(true) }}>
             <Plus className="w-4 h-4 mr-1" />新建事件
           </Button>
         </div>