Board Thread:General Discussion/@comment-5824906-20130318235343/@comment-24674051-20161228180142

I'm willing to accept 0815, or August 15, for Henry's birthday, since it was stated in the episode that the code was 0815, and that Regina used his Birthday.

With that, the only confirmed Birthdates are Emma, Zelena (at least month and day,not year), and Henry. All others are speculative at this point.

And you're right, Math is a concept foreign to the writer's room.