The 20th century began on January 1, 1901 and ended on December 31, 2000. This is the standard historical convention because there was no year 0 in the Gregorian calendar, so centuries start with year 1 rather than year 0.

Quick Scoop

  • Start: January 1, 1901.
  • End: December 31, 2000.
  • Why people get confused: Many assume “1900” starts the century, but 1900 is actually the last year of the 19th century.

If you want, I can also explain why some people say 1900 in a sentence or two.