The driver lacks the ability to use client-side timestamps.

While, of course, it is possible to set a custom timestamp for a statement via the CQL USING TIMESTAMP clause, the Datastax Java driver also allows to:

• Programmatically set the timestamp for the query - Statement.setQueryTimestamp(),
• Use a client-side timestamp generator which automatically generates a new timestamp just before sending the statement.

Source: https://docs.datastax.com/en/developer/java-driver/4.10/manual/core/query_timestamps/