Tonight I prepped my game save for this Valentine's Day achievement and found what I believe to be an error in the game.
On the Calendar, with 2013 as the year, it has Mother's Day as 5/13/2013.
In reality, it is 5/12/2013. While I didn't go back to him and verify that 5/12/2013 worked because I switched my years to 2012 after it not registering 3 times, the date May 13th is circled on his calendar.
Thought I'd bring this up just because it caused me some frustration, and likely it will cause others some grief as well.