December 21, 12:42 UTC: Winter solstice in the Northern Hemisphere, Summer solstice in the Southern Hemisphere
- 69 - Vespasian became the fourth Roman Emperor in the Year of the four emperors, and first of the Flavian dynasty.
- 1913 - Arthur Wynne published the first crossword puzzle in the New York World.
- 1958 - Charles de Gaulle was elected as the first President of the Fifth Republic of France.
- 1988 - Pan Am Flight 103: A terrorist bomb exploded and destroyed a Boeing 747 over Lockerbie, Scotland, killing 270, including 11 on the ground.
Recent days: December 20 – December 19 – December 18
December 21, 12:42 UTC: Winter solstice in the Northern Hemisphere, Summer solstice in the Southern Hemisphere
- 69 - Vespasian became the fourth Roman Emperor in the Year of the four emperors, and first of the Flavian dynasty.
- 1913 - Arthur Wynne published the first crossword puzzle in the New York World.
- 1958 - Charles de Gaulle was elected as the first President of the Fifth Republic of France.
- 1988 - Pan Am Flight 103: A terrorist bomb exploded and destroyed a Boeing 747 over Lockerbie, Scotland, killing 270, including 11 on the ground.
Recent days: December 20 – December 19 – December 18