Here's how to answer:
Directly:
* "Nací el [date]" (I was born on [date])
Example:
* "Nací el 15 de abril de 1990." (I was born on April 15th, 1990.)
Less Direct:
* "Yo nací en [year]" (I was born in [year])
Example:
* "Yo nací en 1990." (I was born in 1990.)
Formal:
* "Mi fecha de nacimiento es [date]" (My date of birth is [date])
Example:
* "Mi fecha de nacimiento es el 15 de abril de 1990." (My date of birth is April 15th, 1990.)
Remember to use the correct gender agreement for the word "nací" (I was born) or "naciste" (you were born).
Let me know if you have any other questions!