Add timestamp in Firestore documents

Question

I'm newbie to Firestore. Firestore docs says...

Important: Unlike "push IDs" in the Firebase Realtime Database, Cloud Firestore auto-generated IDs do not provide any automatic ordering. If you want to be able to order your documents by creation date, you should store a timestamp as a field in the documents.

Reference: https://firebase.google.com/docs/firestore/manage-data/add-data

So do I have to create key name as timestamp in document? Or created is suffice to fulfill above statement from Firestore documentation.

{     "created": 1534183990,     "modified": 1534183990,     "timestamp":1534183990 } 

Answer 1

firebase.firestore.FieldValue.serverTimestamp() 

Whatever you want to call it is fine afaik. Then you can use orderByChild('created').

I also mostly use firebase.database.ServerValue.TIMESTAMP when setting time

ref.child(key).set({   id: itemId,   content: itemContent,   user: uid,   created: firebase.database.ServerValue.TIMESTAMP  }) 

Answer 2

Use firestore Timestamp class, firebase.firestore.Timestamp.now().

Since firebase.firestore.FieldValue.serverTimestamp() does not work with add method from firestore. Reference