The twenty-first day of December.
- 1620: Plymouth Colony: William Bradford and the Mayflower Pilgrims land on what is now known as Plymouth Rock in Plymouth, Massachusetts.
- 1973: The Geneva Conference on the Arab-Israeli conflict opens.
- 1995: The city of Bethlehem passes from Israeli to Palestinian control.
- 1118: Thomas Becket, Lord Chancellor of England and Archbishop of Canterbury (d. 1170)
- 1596: - Petro Mohyla, Moldovan Orthodox Metropolitan Bishop of Kiev and Galicia (d. 1646)
- 1603: Roger Williams, English theologian and colonist (d. 1684)
- 1811: Archibald Campbell Tait, Archbishop of Canterbury (d. 1882)
- 72: Thomas the Apostle
- 1504: Bertold von Henneberg-Römhild, German archbishop and elector (b. 1442)
- 1597: Petrus Canisius, Dutch Jesuit (b. 1521)
- O Oriens (O Sunrise)
- Saint Petrus Canisius - the patron saint of half days and not making or recieving phone calls
- formerly feast day of Thomas the apostle