Christmas day is the only one on which mass is celebrated three times. This custom, which is peculiar to the Western Church, was established in the VIIth century when the Pope celebrated the Christmas office in a number of churches around Rome. During Charlemagne’s reign, this custom spread throughout his empire but it was only in the XIXth century that it became usual to celebrate the three masses consecutively.
In reference to the content of the respective Gospels in the Roman missal for these three masses, the faithful came to
call the first mass the "Angels’ Mass", the second the "Shepherds’ Mass" and the third the "Mass of the Divine
Word". The masses are better known under the names of: Midnight Mass, Dawn Mass and Christmas Day Mass.