Birthday wishes to daughter: Hello

Hello, Do you say "on my birthday " or "at my birthday ". Apparently you can say both. In which context do you use "on" and "at"? Many thanks. A. What's your birthday ? (What is your birthday ?) It is a question asking about the date you were born, and the answer would be, say, March 29, 1999. (Note: It is the same as "When was your birthday ?") B. When is your birthday ? It is a question asking about the anniversary day of birth, and the answer would be, say, March 29. Hi Dark90, Someone's birthday is this month. (Their birthday is in May. It is May now.) Someone's birthday is on this month. Someone's birthday is in this month. (I can't think of many uses for this. Example: Good news for all those born in May! If your birthday is in this month, you are eligible for a special gift from our sponsors!) Hi, guys, what's the difference between " birthday " and "birth date"? Is it a stupid question? In my opinion, all the people only have one birth date the whole life long, but everyone has a birthday every year.