On Christmas Eve, we celebrate the “Children’s Mass” at 4:30 PM, and the “Midnight Mass” at 7:30 PM. On Christmas Day, we celebrate Mass at 9:00 AM and 11:00 AM.
Christmas or Christmas Day is an annual festival commemorating the birth of Jesus Christ, observed most commonly on December 25 as a religious and cultural celebration among billions of people around the world. A feast central to the Christian liturgical year, it is prepared for by the season of Advent or the Nativity Fast and initiates the season of Christmastide, which historically in the West lasts twelve days and culminates on Twelfth Night; in some traditions, Christmastide includes an Octave. Christmas Day is a public holiday in many of the world’s nations, is celebrated culturally by a large number of non-Christian people, and is an integral part of the holiday season, while some Christian groups reject the celebration. In several countries, celebrating Christmas Eve on December 24 has the main focus rather than December 25, with gift-giving and sharing a traditional meal with the family.
While the month and date of Jesus’ birth are unknown, by the early-to-mid 4th century, the Western Christian Church had placed Christmas on December 25, a date later adopted in the East. Today, most Christians celebrate Christmas on the date of December 25 in the Gregorian calendar, which has been adopted almost universally in the civil calendars used in countries throughout the world. However, some Eastern churches celebrate Christmas on the December 25 of the older Julian calendar, which currently corresponds to January 7 in the Gregorian calendar, the day after the Western Christian Church celebrates the Epiphany. This is not a disagreement over the date of Christmas as such, but rather a preference of which calendar should be used to determine the day that is December 25. In the Council of Tours of 567, the Church “declared the twelve days between Christmas and Epiphany to be one unified festal cycle”, thus giving significance to both December 25 and January 6.
More at Wikipedia.org.