diff --git a/src/components/EventDetail.vue b/src/components/EventDetail.vue
index 1cca6a2..9ce48df 100644
--- a/src/components/EventDetail.vue
+++ b/src/components/EventDetail.vue
@@ -1,7 +1,7 @@
 <script setup>
 import { ref, watch } from 'vue'
 import { useCalendar } from '../composables/useCalendar.js'
-import { DOW_EN } from '../lib/weekday.js'
+import { DOW, DOW_EN } from '../lib/weekday.js'
 import OccurrenceGrid from './OccurrenceGrid.vue'
 
 const { selectedEvent, updateEvent, deleteEvent, splitEvent, toggleOccurrence } = useCalendar()
@@ -142,7 +142,7 @@ function onToggleOcc(date) {
           <label>星期 (BYDAY)</label>
           <select v-model="form.byday">
             <option v-for="(d, i) in DOW_EN" :key="d" :value="d">
-              {{ ['周日','周一','周二','周三','周四','周五','周六'][i] }}
+              {{ DOW[i] }}
             </option>
           </select>
         </div>
diff --git a/src/components/EventList.vue b/src/components/EventList.vue
index 99c570c..a544252 100644
--- a/src/components/EventList.vue
+++ b/src/components/EventList.vue
@@ -1,15 +1,12 @@
 <script setup>
 import { useCalendar } from '../composables/useCalendar.js'
 import { DOW } from '../lib/weekday.js'
+import { toDate } from '../lib/date.js'
 
-const { state, stats, addEvent } = useCalendar()
-
-function selectEvent(uid) {
-  state.selectedUid = uid
-}
+const { state, stats, addEvent, selectEvent } = useCalendar()
 
 function dowFor(ev) {
-  return DOW[new Date(ev.dtstartDate + 'T00:00:00').getDay()]
+  return DOW[toDate(ev.dtstartDate).getDay()]
 }
 </script>
 
diff --git a/src/components/HeaderBar.vue b/src/components/HeaderBar.vue
index bd29e5e..46e844a 100644
--- a/src/components/HeaderBar.vue
+++ b/src/components/HeaderBar.vue
@@ -2,7 +2,7 @@
 import { useCalendar } from '../composables/useCalendar.js'
 import { ref } from 'vue'
 
-const { state, canUndo, canRedo, organize, undo, redo, serialize, markSaved } = useCalendar()
+const { state, canUndo, canRedo, organize, undo, redo, serialize, markSaved, loadFile } = useCalendar()
 const fileInput = ref(null)
 
 function onOrganize() {
@@ -19,7 +19,6 @@ function onImport() {
 function onFilePicked(e) {
   const file = e.target.files[0]
   if (!file) return
-  const { loadFile } = useCalendar()
   loadFile(file).catch((err) => alert('解析失败：' + (err.message || err)))
   e.target.value = ''
 }
diff --git a/src/components/OccurrenceGrid.vue b/src/components/OccurrenceGrid.vue
index 34d372b..f09b2d9 100644
--- a/src/components/OccurrenceGrid.vue
+++ b/src/components/OccurrenceGrid.vue
@@ -1,6 +1,7 @@
 <script setup>
 import { computed } from 'vue'
 import { DOW } from '../lib/weekday.js'
+import { toDate } from '../lib/date.js'
 import { expandOccurrences } from '../lib/recur.js'
 
 const props = defineProps({
@@ -11,7 +12,7 @@ const emit = defineEmits(['toggle'])
 const occurrences = computed(() => expandOccurrences(props.event))
 
 function dowFor(dateStr) {
-  return DOW[new Date(dateStr + 'T00:00:00').getDay()]
+  return DOW[toDate(dateStr).getDay()]
 }
 </script>
 
diff --git a/src/composables/useCalendar.js b/src/composables/useCalendar.js
index 0f8d841..14cf58c 100644
--- a/src/composables/useCalendar.js
+++ b/src/composables/useCalendar.js
@@ -1,6 +1,8 @@
 import { reactive, computed } from 'vue'
 import { parseICS, serializeICS } from '../lib/ical-io.js'
 import { organize as organizeEvents } from '../lib/organize.js'
+import { createEvent, cloneEvent } from '../lib/event-factory.js'
+import { splitRecurringEvent } from '../lib/split.js'
 
 const MAX_HISTORY = 50
 
@@ -20,8 +22,8 @@ const state = reactive({
 // ------------------------------------------------------------------ //
 function snapshot() {
   return {
-    meta: state.meta ? JSON.parse(JSON.stringify(state.meta)) : null,
-    events: JSON.parse(JSON.stringify(state.events)),
+    meta: state.meta ? cloneEvent(state.meta) : null,
+    events: state.events.map(cloneEvent),
     selectedUid: state.selectedUid,
   }
 }
@@ -33,8 +35,8 @@ function pushHistory() {
 }
 
 function restore(snap) {
-  state.meta = snap.meta ? JSON.parse(JSON.stringify(snap.meta)) : null
-  state.events = JSON.parse(JSON.stringify(snap.events))
+  state.meta = snap.meta ? cloneEvent(snap.meta) : null
+  state.events = snap.events.map(cloneEvent)
   state.selectedUid = snap.selectedUid
 }
 
@@ -54,6 +56,10 @@ function loadFile(file) {
   })
 }
 
+function selectEvent(uid) {
+  state.selectedUid = uid
+}
+
 function organize() {
   if (state.events.length === 0) return
   pushHistory()
@@ -81,23 +87,7 @@ function deleteEvent(uid) {
 
 function addEvent() {
   pushHistory()
-  const today = new Date()
-  const y = today.getFullYear()
-  const m = String(today.getMonth() + 1).padStart(2, '0')
-  const d = String(today.getDate()).padStart(2, '0')
-  const ev = {
-    uid: crypto.randomUUID(),
-    summary: '新日程',
-    location: '',
-    description: '',
-    dtstartDate: `${y}-${m}-${d}`,
-    dtstartTime: '09:00',
-    dtendTime: '10:00',
-    tzid: 'UTC',
-    rrule: null,
-    exdates: [],
-    _raw: { dtstamp: new Date().toISOString().replace(/[-:]/g, '').split('.')[0] + 'Z' },
-  }
+  const ev = createEvent()
   state.events.push(ev)
   state.selectedUid = ev.uid
   state.dirty = true
@@ -107,34 +97,11 @@ function splitEvent(uid, splitDate) {
   const ev = state.events.find((e) => e.uid === uid)
   if (!ev || !ev.rrule) return
 
-  // Snap splitDate to the next grid point >= splitDate
-  const step = ev.rrule.freq === 'WEEKLY' ? 7 * (ev.rrule.interval || 1) : (ev.rrule.interval || 1)
-  const start = new Date(ev.dtstartDate + 'T00:00:00')
-  let snap = new Date(splitDate + 'T00:00:00')
-  // Advance snap to the next grid point on or after splitDate
-  while (snap < start || ((snap - start) / (24 * 3600 * 1000)) % step !== 0) {
-    if (snap < start) { snap = new Date(start); break }
-    snap.setDate(snap.getDate() + 1)
-    if (snap > new Date(ev.rrule.untilDate + 'T00:00:00')) return // out of range
-  }
-  const snapStr = `${snap.getFullYear()}-${String(snap.getMonth() + 1).padStart(2, '0')}-${String(snap.getDate()).padStart(2, '0')}`
-
-  // Part A: rrule.untilDate = day before snap (previous grid point)
-  const prevGrid = new Date(snap)
-  prevGrid.setDate(prevGrid.getDate() - step)
-  const prevStr = `${prevGrid.getFullYear()}-${String(prevGrid.getMonth() + 1).padStart(2, '0')}-${String(prevGrid.getDate()).padStart(2, '0')}`
+  const parts = splitRecurringEvent(ev, splitDate)
+  if (!parts) return
 
   pushHistory()
-
-  const partA = JSON.parse(JSON.stringify(ev))
-  partA.rrule = { ...ev.rrule, untilDate: prevStr }
-  partA.exdates = ev.exdates.filter((d) => d < splitDate)
-
-  const partB = JSON.parse(JSON.stringify(ev))
-  partB.uid = crypto.randomUUID()
-  partB.dtstartDate = snapStr
-  partB.exdates = ev.exdates.filter((d) => d >= splitDate)
-
+  const [partA, partB] = parts
   const idx = state.events.findIndex((e) => e.uid === uid)
   state.events.splice(idx, 1, partA, partB)
   state.selectedUid = partB.uid
@@ -199,6 +166,7 @@ export function useCalendar() {
     isLoaded,
     stats,
     loadFile,
+    selectEvent,
     organize,
     updateEvent,
     deleteEvent,
diff --git a/src/lib/ical-io.js b/src/lib/ical-io.js
index ac296e0..70d1e21 100644
--- a/src/lib/ical-io.js
+++ b/src/lib/ical-io.js
@@ -1,4 +1,5 @@
 import ICAL from 'ical.js'
+import { pad2, parseISODate } from './date.js'
 
 // ------------------------------------------------------------------ //
 // Timezone registration (ical.js does not bundle IANA zones)
@@ -13,17 +14,14 @@ function registerTimezones(vcalendar) {
 }
 
 // ------------------------------------------------------------------ //
-// Helpers
+// ICAL.Time <-> plain string helpers
+// (ICAL.Time exposes .year/.month/.day/.hour/.minute directly)
 // ------------------------------------------------------------------ //
-function pad2(n) {
-  return String(n).padStart(2, '0')
-}
-
-function timeToISODate(t) {
+function icalTimeToISODate(t) {
   return `${t.year}-${pad2(t.month)}-${pad2(t.day)}`
 }
 
-function timeToHHMM(t) {
+function icalTimeToHHMM(t) {
   return `${pad2(t.hour)}:${pad2(t.minute)}`
 }
 
@@ -67,7 +65,7 @@ function parseEvent(veventComp) {
   const exdates = []
   for (const prop of veventComp.getAllProperties('exdate')) {
     for (const t of prop.getValues()) {
-      exdates.push(timeToISODate(t))
+      exdates.push(icalTimeToISODate(t))
     }
   }
 
@@ -83,9 +81,9 @@ function parseEvent(veventComp) {
     summary: veventComp.getFirstPropertyValue('summary') || '',
     location: veventComp.getFirstPropertyValue('location') || '',
     description: veventComp.getFirstPropertyValue('description') || '',
-    dtstartDate: timeToISODate(start),
-    dtstartTime: timeToHHMM(start),
-    dtendTime: timeToHHMM(end),
+    dtstartDate: icalTimeToISODate(start),
+    dtstartTime: icalTimeToHHMM(start),
+    dtendTime: icalTimeToHHMM(end),
     tzid,
     rrule,
     exdates,
@@ -125,11 +123,6 @@ export function parseICS(text) {
 // ------------------------------------------------------------------ //
 // Helpers for serialization
 // ------------------------------------------------------------------ //
-function parseISODate(s) {
-  const [y, m, d] = s.split('-').map(Number)
-  return { year: y, month: m, day: d }
-}
-
 function parseHHMM(s) {
   const [h, m] = s.split(':').map(Number)
   return { hour: h, minute: m }