December 31 is the 365th day of the year (366th in leap years) in the Gregorian calendar. It is widely known as New Year's Eve since the following day isNew Year's Day. It is the last day of the year.
1955 – The General Motors Corporation becomes the first U.S. corporation to make over US$1 billion in a year.
- 1960 – The farthing coin ceases to be legal tender in the United Kingdom.
- 1961 – RTÉ Ireland's state broadcaster launches its first national television service.
- 1963 – The Central African Federation officially collapses and splits into Zambia, Malawi and Rhodesia.
- 1965 – Jean-Bédel Bokassa, leader of the Central African Republic army, and his military officers begins a coup d'état against the government of President David Dacko.
- 1981 – A coup d'état in Ghana removes President Hilla Limann's PNP government and replaces it with the Provisional National Defence Council led by Flight Lieutenant Jerry Rawlings.
- 1983 – The AT&T Bell System is broken up by the United States Government.
- 1983 – In Nigeria a coup d'état led by Major General Muhammadu Buhari ends the Nigerian Second Republic.
- 1986 – A fire at the Dupont Plaza Hotel in San Juan, Puerto Rico, kills 97 and injures 140.
- 1991 – All official Soviet Union institutions have ceased operations by this date and the Soviet Union is officially dissolved.
- 1992 – Czechoslovakia is peacefully dissolved in what is dubbed by media as the Velvet Divorce, resulting in the creation of the Czech Republic and Slovakia.
- 1994 – This date is skipped altogether in Kiribati as the Phoenix Islands and Line Islands change time zones from UTC−11:00 to UTC+13:00 and UTC-10:00 to UTC+14:00, respectively.