How come we are in the 21st century if we are in the 2000s and not 2100s?

Question

How come we are in the 21st century if we are in the 2000s and not 2100s?

In: Other

Answer 1

The day from your birth up to your first birthday is your first year on earth.

So [0, 1) is your first year.

[0, 10) is your first decade

[0, 100) is your first century

[100, 200) your second century

…

[2000, 2100) your twenty-first century

Now apply this to a calendar instead of your birthday and you have your answer:

The number marks the years that have – passed – while the term “21st century” marks the time span that is – going on currently.