I have a silly question...when I want to ask somebody about his date of birth, including the year, which of the following(s) is(are) correct?
1. When is your birthday?
2. When was your birthday?
3. What is your date of birth?
4. What was your date of birth?
5. What is the date of your birth?
6. What was the date of your birth?
Can anyone answer me? Thanks a lot.
They are all correct, although to me numbers 4 and 6 sound slightly unnatural. Which one to use depends on the context and what you are trying to find out.
To "When is your birthday?" "February" might well be an acceptable answer. But "What is your date of birth?" definitely requires a precise date.