Latter Day Ain't
A non-devout / faux member of the Church of Jesus Christ of Latter Day Saints. A Jack Mormon. One who is Mormon by culture, but does not have a testimony of the church or who does not live by its precepts.
Person 1: Dude! Can you believe that Jack is a Mormon and he voted for Obama and against Proposition 8?

Person 2: Yeah. Jack is total Latter Day Ain't!