Christmas is observed on December 25 to commemorate the birth of Jesus, the central figure of Christianity. The date is not known to be Jesus’s actual birthday, and may have been chosen to correspond with either the day nine months after early Christians believed Jesus was conceived, the date of the winter solstice on the ancient Roman calendar, or one of various ancient winter festivals. In Christianity, Christmas marks the beginning of the larger season of Christmastide, which lasts 12 days.