We switched to sending dates as string in to presumably work-around the fact that pre-1.2.16 versions of Cassandra didn't allowed negative timestamp and thus pre-epoch timestamps.
But in doing so we've made things worth because https://issues.apache.org/jira/browse/CASSANDRA-6395 (which is not fixed at all on C* 1.2) gets in the way. Concretely, date with the query builder are just broken against 1.2 and again any C* before 2.0.4.
So was overall misguided and I've reverted it. All this means is that those that want to use pre-epoch dates with C* 1.2 should update to 1.2.16, but that's certainly better than "dates are completely broken before C* 2.0.4".