DEC-1: This is World AIDS Day. AIDS has killed about 15 million people; over 50 million are infected -- mostly among African heterosexuals.

DEC-6: In Canada, this is the National Day of Remembrance and Action on Violence Against Women. On 1989-DEC-6, a deranged gunman, entered the École Polytechique de Montréal. His application to the school had been rejected. He blamed feminists for ruining his life. He shot 27 people: 23 women and 4 men. 14 women died. All the men survived.

DEC-8: Bodhi Day (a.k.a. Rohatsu) is when Buddhist celebrate the enlightenment of the Buddha in 596 BCE. It is sometimes celebrated on the Sunday before DEC-8. ₄

DEC-10: This is Human Rights Day, DEC-10, the 52^nd anniversary of the signing of the United Nations Universal Declaration of Human Rights.  "The 1000 Lamp Mandala Ceremony" is celebrated around the world to promote peace in Tibet and elsewhere.

DEC-22: The first day of an 8 day Jewish festival of Hanukkah, (a.k.a. Chanukah, Feast of Lights, Feast of Dedication.) It recalls the war fought by the Maccabees in the cause of religious freedom.

DEC-21: The Winter Solstice happens on this day at 13:37 ET. It is celebrated by many Aboriginal and Neopagan religions around the world. It is called Yule by Wiccans, who consider it one of the four minor Sabbats. The longest night and shortest daytime occurs on this day.

DEC-25: Celebration of Christmas, the nominal birth date of Jesus Christ, by the western churches which follow the Gregorian calendar. Most theologians believe that Jesus was born between 4 and 7 BCE, perhaps in the fall.

DEC-26: This is the first day of a week-long celebration of Kwanza (a.k.a. Kwanzaa, Quansa) - a cultural holiday celebrating African-American heritage. "Kwanza" is a Swahili word for "the first," or "the first fruits of the harvest". 

DEC-26: Boxing Day is celebrated in Australia, the Bahamas, Jamaica, Canada, New Zealand and the UK. It is apparently related to an old custom of giving cash or presents to poor people. However, nobody really knows for certain why the "Box" got into "Boxing Day." Theories abound. It is listed in the Canada Labour Code as a holiday.

DEC-27: The probable date of Id al-Fitr, (a.k.a. Eid-ul-Fitr) the last day of Ramadan. This is the holiest period in the Islamic year. It recalls the lunar month in which the Qura'n was revealed to humanity. The end of Ramadan may be offset from this day, because it is dependent on the sighting of the crescent moon.

DEC-31: New Year's Eve. This is really the last day of the millennium. Others regard 1999-DEC-31 as the last day.