How can I know what constellation I am? See the lunar calendar or the solar calendar? My ID card is1991March 29th, but my birthday is February 12.

Most ID cards are solar calendars, but some people are lunar calendars.

So I don't know yours. You can ask your parents.

Now the constellation doesn't need the old calendar, so it is calculated according to the solar calendar.

If your solar calendar is March 29th, you are Aries.

If it is February 12, then you are Aquarius.

But I think you are more likely to be Aries, because few people celebrate their birthdays in the lunar calendar.