[BigSkyFreeper]

It’s like the 21st Century didn’t start until 2001. I remember discussions leading up to 2000 on that.

[Petronski]

It’s like the 21st Century didn’t start until 2001.

But that's an ordinal definition of century: first century, eleventh century, eighteenth century, etc.

As far as informal, colloquial definitions of cardinal decades, it is ridiculous to say the eighties did not start until 1981.

[hellbender]

Aha. So now we know why the dreaded Y2K collapse never happened when 2000 AD started!