There is a restriction on setting your birthday:
Oops! There was a problem updating your profile:
- Birthday must be after 1920/01/01
I realize the number of 90 year old users is small, but shouldn't the restriction be a bit more relaxed, such as larger than any known living person? Either 120 or 150 seems appropriate.
For example, my grandfather turns 90 next year (and just barely misses the current cutoff), but I can't imagine he's the only one around that age who is computer literate and still active enough to be interested in (the increasingly broad range of) SE sites. I don't think he has contributed yet (mostly because of the comment restriction, I'd see him commenting before asking or answering), but I have emailed him with links that I know he's read.
Incidentally, the error message is wrong: birthday must be after 1919/12/31 and using the next day is accepted.