Christmas, also referred to as Christmas Day, is an annual holiday celebrated on December 25 that commemorates the birth of Jesus of Nazareth.

The day marks the beginning of the larger season of Christmastide, which lasts twelve days. The nativity of Jesus, which is the basis for the anno Domini system of dating, is thought to have occurred between 7 and 2 BC. December 25 is not known to be Jesus' actual date of birth, and the date may have been chosen to correspond with either a Roman festival or the winter solstice.