That's because BlackBerry feels that birthdays have been over celebrated for far too many years. Honest though it should but I don't know that it ever will without a third party app.
That said the current update has some big calendar bugs. So if it could notify you it probably wouldn't anyway
A Blackberry doesn't remind you of birthdays because it's not a woman.
Women do birthday's and anniversaries. They are available, but expensive; avoid the Pay as you go type. They require many types of expensive cases and can never decide which one to use, so will demand yet another. Get a contract with unlimited minutes; you'll need one trust me.
You'll never forget a birthday again; if you do, woe betide.....
:@@"+; ;;_::!!!!!!!!!!!!!!!!!!!!!!!! Settings, accounts, add account. Add your outlook or gmail email address and calendar and contacts. The phone should do the rest. If you don't have an outlook.com account, just get one. They're Free. If you don't want to do that, just tap the middle media key and and say 'add to calendar: 22nd feb all day, john's birthday. Repeat yearly'