date is introduced in Cassandra 2.2.0. You are currently using Cassandra 2.1.12
I have to use v. 2.1.12, which data type is better for a birthday column (date_of_birth), then? Since, the Date data type is unknown in this version, and I just need the date, not date-time.
Just use the date-time and disregard the time component when you insert or use the results (0 it up). that way you get basically a Date component, takes a little more space but sorting and everything else goes smoothly and as you would expect.