It started on Jan 1st 1900 and ended at midnight december 1999 .
When Did The 20th Century Start And End?
It actually started on Jan 1st 1901 and ended on dec 31st 2000.
The 20th century began in 1900 and ended at the end of 1999.
The 20th century is like 2000 2001 2002 2003... And then after a long time... 2999 and then once it hits 3000 it is the 30th century.