fix hydration error

src/client/theme-default/components/VPDocFooterLastUpdated.vue

@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import { ref, computed, watchEffect } from 'vue'
+import { ref, computed, watchEffect, onMounted } from 'vue'
 import { useData } from '../composables/data'
 
 const { theme, page, lang } = useData()
@@ -8,8 +8,12 @@ const date = computed(() => new Date(page.value.lastUpdated!))
 const isoDatetime = computed(() => date.value.toISOString())
 const datetime = ref('')
 
-watchEffect(() => {
-  datetime.value = date.value.toLocaleString(lang.value)
+// set time on mounted hook to avoid hydration mismatch due to
+// potential differences in timezones of the server and clients
+onMounted(() => {
+  watchEffect(() => {
+    datetime.value = date.value.toLocaleString(lang.value)
+  })
 })
 </script>