This is causing an error,

==  AddTagDate: migrating =====================================================
-- execute("ALTER TABLE tags ADD COLUMN last_update timestamp without time zone;")
rake aborted!
An error has occurred, all later migrations canceled:

Mysql2::Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'without time zone' at line 1: ALTER TABLE tags ADD COLUMN last_update timestamp without time zone;