century

So, when did the 21st century begin?

Base data: hour. 1 century = 100 years
Said to have originated the year Christ was born

The oddly complicated century

A century is 100 years. In the west, it is used as a unit of time. It is currently the 21st century. Therefore, do you know what century it was on 1st January, 2000? For example, when did the 100s BC start and end? Come to think of it, a century is oddly complicated.