Modified version I’m using with LiveView now :
<time id="updated_at" datetime="2020-06-30 12:21:17Z"></time>
<span id="updated_at_view" phx-update="ignore"></span>
<script>
const view_element = document.getElementById('updated_at_view');
document.addEventListener('phx:update', () => {
const source_element = document.getElementById('updated_at');
view_element.innerText = new Date(source_element.getAttribute('datetime')).toLocaleString();
})
</script>
