There are many religious holidays in December however I did not fully realize how many until I saw this list. Hence why we say "Happy Holidays" to individuals instead of just mentioning the holiday that we celebrate. I found the list on the Diversity Resources calendar.
December is often seen as the last month of the year, but that’s true only of the western Gregorian calendar. Chinese, Islamic, Jewish and other calendars define the first and last month differently.
Nevertheless, December includes important holidays and events among these religions and among other traditions. For a complete list, see our online diversity calendar.
December 1-24: Advent, a Christian season of celebration leading up to the birth of Christ.
December 8: Immaculate Conception of Mary, the Feast of the Immaculate Conception celebrates the solemn celebration, by various Christian denominations, of belief in the Immaculate Conception of the Blessed Virgin Mary.
December 12: Feast of Our Lady of Guadalupe, a religious holiday in Mexico commemorating the appearance of the Virgin Mary near Mexico City in 1531.
December 13: St. Lucia’s Day, a religious festival of light in Scandinavia and Italy commemorating the martyrdom of St. Lucia, a young Christian girl who was killed for her faith in 304 C.E. She secretly brought food to persecuted Christians in Rome while wearing a wreath of candles on her head so both her hands would be free.
December 16-24: Las Posadas, a nine-day celebration in Mexico commemorating the trials Mary and Joseph endured during their journey to Bethlehem.
December 21: Yule Winter Solstice, celebrated by Pagans and Wiccans. The shortest day of the year represents a celebration focusing on rebirth, renewal and new beginnings as the sun makes its way back to the Earth. A solstice is an astronomical event that happens twice each year when the sun reaches its highest position in the sky.
December 22-30: Hanukkah, a Jewish holiday that is celebrated around the world for eight days and nights. Hanukkah celebrates the victory of the Maccabees, or Israelites, over the Greek-Syrian ruler, Antiochus, approximately 2,200 years ago.
December 25: Christmas Day, the day that many Christians associate with Jesus’ birth.
December 26: Boxing Day, a secular holiday celebrated in the U.K., Canada, Ireland, Australia, New Zealand, Hong Kong and South Africa.
December 26-January 1: Kwanzaa, an African-American holiday started by Maulana Karenga in 1966 to celebrate universal African-American heritage.
December 26: Zartosht No-Diso (Death of Prophet Zarathushtra), a day of remembrance in the Zoroastrian religion. It is a commemoration of the death anniversary of the prophet Zoroaster, or Zarathushtra.
December 26: St. Stephen’s Day, a day to commemorate St. Stephen, the first Christian martyr, or protomartyr.
December 27: St. John’s Day, Apostle and Evangelist, feast day for St. John celebrated by Christian denominations.
December 28: Feast of the Holy Innocents, a Christian feast in remembrance of the massacre of young children in Bethlehem by King Herod the Great in his attempt to kill the infant Jesus.
December 29: Feast of the Holy Family, a liturgical celebration in the Catholic Church in honor of Jesus, his mother and his foster father, St. Joseph as a family. The primary purpose of this feast is to present the Holy Family as a model for Christian families.
December 31: Watch Night, a day for Christians to review the year that has passed, make confessions, and then prepare for the year ahead by praying and resolving.
