Christmas is an annual festival commemorating the birth of Jesus Christ observed on December 25. It is a public holiday in many countries and celebrated by billions around the world. Popular modern customs include gift giving, Christmas music and decorations like trees, lights, and nativity scenes. Santa Claus and other figures associated with gift giving during Christmas have evolved over time in popular culture. Christmas traditions vary by country but often involve religious services, special meals, exchanging greetings and presents. In California, the Christmas season begins around late November with shopping and decorations extending into late fall. In El Salvador, children celebrate with fireworks while families have parties with traditional foods and gather to open presents after midnight on Christmas Day.