perf: add `<time>` tag

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

@@ -22,9 +22,7 @@ const control = usePrevNext()
           {{ editLink.text }}
         </VPLink>
       </div>
-      <div v-if="page.lastUpdated">
-        <VPLastUpdated />
-      </div>
+      <VPLastUpdated v-if="page.lastUpdated"/>
     </div>
 
     <div class="prev-next">

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

@@ -3,19 +3,24 @@ import { ref, onMounted, watchEffect } from 'vue'
 import { useData } from 'vitepress'
 
 const { theme, page } = useData()
-
+const data = new Date(page.value.lastUpdated!)
+const isoDatetime = data.toISOString()
 const datetime = ref('')
+
 onMounted(() => {
   watchEffect(() => {
     // locale string might be different based on end user
     // and will lead to potential hydration mismatch if calculated at build time
-    datetime.value = new Date(page.value.lastUpdated!).toLocaleString(window.navigator.language)
+    datetime.value = data.toLocaleString(window.navigator.language)
   })
 })
 </script>
 
 <template>
   <div>
-    {{ theme.lastUpdated ?? 'Edit this page' }}: {{ datetime }}
+    {{ theme.lastUpdated ?? 'Edit this page' }}:
+    <time :datatime="isoDatetime">
+      {{ datetime }}
+    </time>
   </div>
 </template>