December 21st is the 355th day of the year (356th in leap years). There are 10 days remaining until the end of the year.
- December 21, 2012 was said to be the end of the world.
- It was also the day Gangnam Style got a billion views on YouTube (this was the first time a YouTube video got a billion views).
- It is one of the most common starting days for a Christmas Break in Finland.