Typically, write timestamps are assigned to data automatically by Cassandra, reflecting the time at which the cluster initially receives the request. However, CQL gives us a mechanism to override the default timestamp and instead choose our own.
To demonstrate, let's say we want to add a location value to the bob user record at a specific timestamp: December 14, 2016 at 10.33.24 UTC. In order to do this, we can use the USING TIMESTAMP clause in our UPDATE query:
UPDATE "users" USING TIMESTAMP 1481711604904000 SET "location" = 'Austin, TX' WHERE "username" = 'bob';
Reading bob's user record back, we can see that it now has the location we specified:
Now let's issue another update to bob's location using a TIMESTAMP ...
