21st Century Naming
Why Is the Current Era Called the 21st Century? Explained

Discover why the era from 2001 to 2100 is called the 21st century, based on the Gregorian calendar and historical century naming conventions.

21st Century Start
Is the Year 2000 Part of the 21st Century?

Discover why the year 2000 is considered the last year of the 20th century, not the first of the 21st century, according to the Gregorian calendar.