firebase timestamps not serverside created

January 1, 2022

I have a chat app in react native using firebase and it is crucial to me that the timestamps are all synchronised and created serversided, not from the client. Clients can have different times depending on the settings on the mobile phone.

I tried out following function to prove my point:

const comparetimes = async () => {
        const timezone1  = firebase.firestore.Timestamp.now();
        const timezone2 = (firebase.firestore.Timestamp.now()).toMillis();
        const timezone3 = Date.now();

        console.log(timezone1);
        console.log(timezone2);
        console.log(timezone3)


    }

What shocked me is the result of this function:

{"nanoseconds": 79000000, "seconds": 1641054839}
1641054839080
1641054839080

Apperently the firebase timestamp is the exact same as Date.now() which is a direct timestamp taken from the mobile phone, and therefore unaccurate.

What can I do to have timestamps not created by the client but by the server, in this example firebase? Do I need to checkout some APIs or is there something I miss here?

>Solution :

When you call Timestamp.now(), it really is just taking the timestamp on the client device. That’s expected.

Read the documentation on how to use server timestamps. You must use the token value returned by firestore.FieldValue.serverTimestamp() in order to tell Firestore to use the current moment in time as the request reaches the server.

When storing timestamps, it is recommended you use the serverTimestamp
static method on the FieldValue class. When written to the database,
the Firebase servers will write a new timestamp based on their time,
rather than the clients. This helps resolve any data consistency
issues with different client timezones:
firestore().doc('users/ABC').update({
  createdAt: firestore.FieldValue.serverTimestamp(),
});