I just read somewhere to take away the frustration of asking for “Date of Birth” you can just ask…
Adrienne Levin

Depends entirely on the data you need, if you needed to know if the user was over 18 for example, you could just ask ‘Over 18? Yes/No’ but if you need to be accurate within 365 days (eg you want to send the user a birthday email) asking ‘Age’ isn’t very helpful.