When does a century begin?

A century begins in a year 01 and ends in a year 00.

For example, the century XX began in 1901 and ended in 2000 and the century XXI started in 2001 and will end in 2100.

However, for some, who recognize the changes made to the Gregorian calendar in 1582, a century begins at a 00 year and ends at a 99 year.

The centuries in history are numbered with Roman numerals and named with ordinals from I through IX (first, second, third…) and with cardinals from X onwards (ten, eleven, twelve, thirteen…).