Quick and simple, use your existing firebase realtime database project to generate an online timestamp. You need a firebase realtime database and a web component, a button and a label.
Blocks
Screen
Firebase
There are many potential uses for this....for example:
what if my all user is authenticated and public user can not read and write then how can i use it with access token... ?
if there is a way to use access token then can i use app's firebase auth token or i need web firebase auth token... ? (i dont know both are same or not)
Shouldn't make any difference. If the Timestamp tag is covered by secure rules, then these should be for any authenticated user to read, and the blocks would apply their idToken in the usual way to return / set the value.