A birthday is the anniversary of the birth of a person, or figuratively of an institution. Birthdays of people are celebrated in numerous cultures, often with birthday gifts, birthday cards, a birthday party, or a rite of passage.
Many religions celebrate the birth of their founders or religious figures with special holidays (e.g. Christmas, Mawlid, Buddha's Birthday, and Krishna Janmashtami).
There is a distinction between birthday and birthdate: the former, except for February 29, occurs each year (e.g. January 15), while the latter is the complete date when a person was born (e.g. January 15, 2001).