If you know my birthday, please don't tell it to others without checking with me first. I don't like this information to be generally known, although I understand that a really persistent person can discover it anyway.
You might be wondering why; after all, it's such a harmless piece of information. Well, the official line I give is that I don't want to encourage people to send me birthday presents, so I prefer that people just considered my birthday to have never existed.
The full story is longer. Every year, I have a small event to celebrate my birthday, usually a dinner with three to four close friends, my shout. I don't know a single guest of mine who doesn't bring a present, so obviously I do receive presents.
For everyone else, I feel bad about accepting a present because I almost feel obliged to invite them to my birthday event in return. My birthday celebrations being so intimate as they are, I'd much rather not receive anything from others than invite them.
Having said that, for my birthday this year, being my 24th (a special event for me), I'm hosting a bigger event, with about ten-odd invitees. If you're on the invitation list, you'll hear from me soon.