When a new century or millenium actually begins

 

New centuries, new milleniums...

Once and for all, follow the logic back to day 1.

A century is equal to 100 years, no more or less. Let's work it out below...

year 0 (day 1 to day 365) is 1st year of that century
year 1 (day 366 to day 730) is 2nd year of that century
year 2 is the 3rd year of that century
year 9 is the 10th year of that century
year 10 is the 11th year of that century
year 50 is the 51st year of that century
year 90 is the 91st year of that century
year 99 is the 100th year of that century.

This means that at the completion of the 99th "labeled" year the century (100 years) has been fulfilled and completed and the next year is the beginning of the new century. That is, the moment the year turns to 100 is the beginning of the new century (2nd). In the same vein, the moment that 2000 began was the beginning of a new century and a new millenium (not the year 2001 as some people believe).

year 100 is the 101st year
year 1000 is the 1001st year
year 2000 is the 2001st year
year 2020 is the 2021st year

The new decade starts at the beginning of the n0 year
The new century starts at the beginning of the n00 year
The new millenium starts at the beginning of the n000 year

Hopefully this ends the debate as to when decades, centuries and milleniums begin.

Happy 21st century!