The 1st day of Christmas typically starts on December 25th, which is also known as Christmas Day. It is a time of celebration and gift-giving that commemorates the birth of Jesus Christ. However, the "12 Days of Christmas" is a traditional song that refers to the 12 days leading up to Christmas, starting on December 25th and ending on January 5th. Each day of the 12 days represents a different aspect of Christmas, such as the 12 drummers drumming, the 11 pipers piping, and so on.