How do you say When is your birthday in Japanese?

Answer 1

You may say, "Anata no otanjoubi wa itsu deshou ka."

Note: please note that when you write it out you are using the hiragana "ha", but when speaking it you say "wa".

あなたの誕生日はいつですか？

Answer 2

anata no tanjobi wa itsu? = when is your birthday