The 1st day of Christmas is December 25th, also known as Christmas Day. It is a Christian holiday that commemorates the birth of Jesus Christ. On this day, people around the world celebrate by exchanging gifts, spending time with loved ones, and enjoying festive activities like caroling, decorating, and feasting. It is a time of joy and togetherness, and many people also celebrate the season leading up to Christmas with traditions like Advent and decorating trees.