December 21 is the 355th day of the year (356th in leap years) in the Gregorian calendar. There are 10 days remaining.
- 2005: "Christmas Who?" premiered in the UK.
- 2014: A sneak-peak for The SpongeBob Movie: Sponge Out of Water aired on Nickelodeon.
- 2017: "Don't Wake Patrick" premiered in Germany only with the original English version.
- December 21 on Wikipedia