diff --git a/package.json b/package.json
index 497bcdf..eed390a 100644
--- a/package.json
+++ b/package.json
@@ -17,6 +17,7 @@
   },
   "dependencies": {
     "pinia": "^3.0.3",
+    "pinia-plugin-persistedstate": "^4.5.0",
     "vue": "^3.5.18"
   },
   "devDependencies": {
@@ -34,4 +35,4 @@
     "vite": "npm:rolldown-vite@latest",
     "vite-plugin-vue-devtools": "^8.0.0"
   }
-}
\ No newline at end of file
+}
diff --git a/src/components/CalendarView.vue b/src/components/CalendarView.vue
index 036cc63..6cad89f 100644
--- a/src/components/CalendarView.vue
+++ b/src/components/CalendarView.vue
@@ -63,7 +63,8 @@ const totalVirtualWeeks = computed(() => {
 })
 
 const initialScrollTop = computed(() => {
-  const targetWeekIndex = getWeekIndex(calendarStore.now) - 3
+  const nowDate = new Date(calendarStore.now)
+  const targetWeekIndex = getWeekIndex(nowDate) - 3
   return (targetWeekIndex - minVirtualWeek.value) * rowHeight.value
 })
 
@@ -76,7 +77,8 @@ const selectedDateRange = computed(() => {
 })
 
 const todayString = computed(() => {
-  const t = calendarStore.now
+  const d = new Date(calendarStore.now)
+  const t = d
     .toLocaleDateString(undefined, { weekday: 'long', month: 'long', day: 'numeric' })
     .replace(/,? /, '\n')
   return t.charAt(0).toUpperCase() + t.slice(1)
diff --git a/src/main.js b/src/main.js
index a7a997b..c74fed5 100644
--- a/src/main.js
+++ b/src/main.js
@@ -2,11 +2,14 @@ import './assets/calendar.css'
 
 import { createApp } from 'vue'
 import { createPinia } from 'pinia'
+import piniaPluginPersistedstate from 'pinia-plugin-persistedstate'
 
 import App from './App.vue'
 
 const app = createApp(App)
 
-app.use(createPinia())
+const pinia = createPinia()
+pinia.use(piniaPluginPersistedstate)
+app.use(pinia)
 
 app.mount('#app')
diff --git a/src/plugins/persist.js b/src/plugins/persist.js
new file mode 100644
index 0000000..c41031d
--- /dev/null
+++ b/src/plugins/persist.js
@@ -0,0 +1,24 @@
+// Simple Pinia persistence plugin supporting `persist: true` and Map serialization.
+export function persistPlugin({ store }) {
+  if (!store.$options || !store.$options.persist) return
+  const key = `pinia-${store.$id}`
+  try {
+    const raw = localStorage.getItem(key)
+    if (raw) {
+      const state = JSON.parse(raw, (k, v) => {
+        if (v && v.__map === true && Array.isArray(v.data)) return new Map(v.data)
+        return v
+      })
+      store.$patch(state)
+    }
+  } catch {}
+  store.$subscribe((_mutation, state) => {
+    try {
+      const json = JSON.stringify(state, (_k, v) => {
+        if (v instanceof Map) return { __map: true, data: Array.from(v.entries()) }
+        return v
+      })
+      localStorage.setItem(key, json)
+    } catch {}
+  })
+}
diff --git a/src/stores/CalendarStore.js b/src/stores/CalendarStore.js
index e12bc1d..741bc5a 100644
--- a/src/stores/CalendarStore.js
+++ b/src/stores/CalendarStore.js
@@ -7,7 +7,7 @@ const MAX_YEAR = 2100
 export const useCalendarStore = defineStore('calendar', {
   state: () => ({
     today: toLocalString(new Date()),
-    now: new Date(),
+    now: new Date().toISOString(), // store as ISO string
     events: new Map(), // Map of date strings to arrays of events
     weekend: getLocaleWeekendDays(),
     config: {
@@ -26,8 +26,9 @@ export const useCalendarStore = defineStore('calendar', {
 
   actions: {
     updateCurrentDate() {
-      this.now = new Date()
-      const today = toLocalString(this.now)
+      const d = new Date()
+      this.now = d.toISOString()
+      const today = toLocalString(d)
       if (this.today !== today) {
         this.today = today
       }
@@ -468,4 +469,19 @@ export const useCalendarStore = defineStore('calendar', {
 
     // NOTE: legacy dynamic getEventById for synthetic occurrences removed.
   },
+  persist: {
+    key: 'calendar-store',
+    storage: localStorage,
+    paths: ['today', 'events', 'config'],
+    serializer: {
+      serialize(value) {
+        return JSON.stringify(value, (_k, v) =>
+          v instanceof Map ? { __map: true, data: [...v] } : v,
+        )
+      },
+      deserialize(value) {
+        return JSON.parse(value, (_k, v) => (v && v.__map ? new Map(v.data) : v))
+      },
+    },
+  },
 })