It absolutely bothers me when my birthday is not remembered by my SO. I do not fail to acknowledge theirs because I do believe it's a special day. It really is as simple as plugging it into your calendar whether electronic with e-mail capabilities or simple paper. I feel the same about wedding/commitment anniversaries. Most holidays don't carry as much importance, but I'm a real stickler for appreciating birthdays and anniversaries. I don't allow the date to go by without a nice, polite reminder if my SO's forgotten, but I also don't hold a grudge and get myself worked up over it for days past.
Anyway. I don't see a problem in reminding someone. Especially if there are going to be hurt feelings later if the date's been forgotten. An ounce of prevention...
Hope your birthday and mothers day turned out for the best.
