Server Timestamps

To store the server's time in a DateTime field, use the serverTimestamp() patch operation. Firestore fills in the time when it applies the write, so the value does not depend on the device clock.

await odm.users('jane').patch(($) => [$.updatedAt.serverTimestamp()]);

It works the same way in bulk writes, batches and transactions:

await odm.runBatch((batch) {
  odm.users.inBatch(batch).patch('jane', ($) => [$.updatedAt.serverTimestamp()]);
});

await odm.runTransaction((tx) async {
  odm.users.inTransaction(tx)('jane').patch(
    ($) => [$.updatedAt.serverTimestamp()],
  );
});

Setting a server time when creating a document

create and set write the model's own values. To add a server time to a new document atomically, queue the write and a patch in one batch:

await odm.runBatch((batch) {
  final users = odm.users.inBatch(batch);
  final id = users.create(newUser);
  users.patch(id, ($) => [$.createdAt.serverTimestamp()]);
});

Use a nullable field

Declare server-set fields as DateTime?. Until the server confirms the write, a listener on the same device sees the field as null.

Reading

Firestore stores the value as a Timestamp. The ODM returns it as a DateTime for the same instant, in local time.