When working with a database on Firebase, is it possible from within an iOS app to check the date(& time) a document was last updated using some standard API? I mean without implementing my own system to know when it was last time touched.
It would be convenient if there was a field "lastUpdate" time-stamp for instance.
Neither the Firebase Realtime Database nor Cloud Firestore automatically adds a user-readable timestamp field to the data for writes.
If you want such a field, you will have to add it yourself, either from the client, or from Cloud Functions.
For a simple example of the latter, which tracks when a node in the database was last modified, see this folder in the functions-samples repo. The main code:
exports.touch = functions.database.ref('/chat/{message}').onWrite(
(change, context) => admin.database().ref('/lastmodified').set(context.timestamp));