- World War III begins.
- World War III ends.
- 21st century at Wikipedia, the free encyclopedia
- 21st century at Memory Alpha, the Star Trek wiki
- 21st century at Memory Beta, the non-canon Star Trek wiki
|v - e - ?||Centuries|
|2nd millennium||19th century|
|3rd millennium||21st century • 22nd century • 23rd century • 24th century • 25th century • 26th century • 27th century • 28th century • 29th century|
|Decades • years • months • days|