You can download an annual calendar which shows when checks/deposits are made, based on birthdays:
http://www.ssa.gov/pubs/calendar.htm
I have auto-deposit, and my monthly is deposited early AM on the exact Wednesday, not the birthday. Mine is the 3rd Wednesday following the 1st Wednesday of the month. It fluctuate between about the 16th and the 22nd, depending on how the days of the month line up.
It goes by the Wednesday nearest your b/day. I got mine on the 4th Wed of the month because my b/day is on the 29th of the month, I got it that way for about 5 years anyway, then they inexplicably changed it to the second day of the month. It's been that way for about 2 years now. It's regular S.S., not disability or anything else. I'm the only person I know who gets an ordinary S.S. check on the second day of the month.