As part of his reform, Caesar instituted January 1 as the first day of the year, partly to honor the month’s namesake: Janus, the Roman god of beginnings, whose two faces allowed him to look back into the past and forward into the future. Romans celebrated by offering sacrifices to Janus, exchanging gifts with one another, decorating their homes with laurel branches and attending raucous parties. In medieval Europe, Christian leaders temporarily replaced January 1 as the first of the year with days carrying more religious significance, such as December 25 (the anniversary of Jesus’ birth) and March 25 (the Feast of the Annunciation); Pope Gregory XIII reestablished January 1 as New Year’s Day in 1582.