A birthday is an occasion when a person or institution celebrates the anniversary of their birth. Birthdays are celebrated in numerous cultures, often with a gift, party, or rite of passage.
Many religions celebrate the birth of their founders with special holidays (e.g. Christmas, Buddha's Birthday).
There is a distinction between birthday and birthdate: The former, other than February 29, occurs each year (e.g. January 15), while the latter is the exact date a person was born (e.g., January 15, 2001).