core / TransactionBuilder / timestamp

# timestamp

`fun timestamp(timestamper: TimestamperService, clock: Clock = Clock.systemUTC()): Unit`

Uses the given timestamper service to request a signature over the WireTransaction be added. There must always be at least one such signature, but others may be added as well. You may want to have multiple redundant timestamps in the following cases:

- Cross border contracts where local law says that only local timestamping authorities are acceptable.

- Backup in case a TSAs signing key is compromised.

The signature of the trusted timestamper merely asserts that the time field of this transaction is valid.