A birthdate is the specific day, month, and year when someone was born. Your birthdate might be March 15, 2014, or October 3, 2013. It's different from your birthday, which is just the month and day you celebrate each year. Your birthday comes around every year, but your birthdate stays the same your whole life.

Birthdates matter for many practical reasons. Schools use them to determine which grade you should be in. Doctors track them to know if you're growing and developing on schedule. Official documents like passports and driver's licenses require your exact birthdate to verify your identity. When you sign up for a library card or create an account online, you might need to enter your birthdate.

People sometimes use the phrase date of birth to mean the same thing, especially on forms and official paperwork. You might see “DOB” as an abbreviation. While sharing your birthday with friends is fun, your complete birthdate is private information that can be important for keeping your identity and accounts safe.