Christmas is an annual festival commemorating the birth of Jesus Christ and celebrated on December 25 among billions of people around the world. This festival is preceded by the season of "Nativity Fasting" or "Advent" and it initiates the season of Christmastide that lasts for twelve days in the West and culminates on the twelfth night. In some traditions, Christmastide includes an octave. Christmas Day, which is a public holiday in many of the world's nations, is celebrated religiously by a majority of Christians, as well as culturally by many of non-Christians, and forms an integral part of the holiday season centered around it.