If you can't even get Centuries correct, your shouldn't even attempt to impose your illogical ideas on decade.
June 1, 1990 was in the 20th Century and we are now in the 21st Century.
You need to rest, must have partied too much in the last decade.
I think you need to rest and re-read what I posted. I said nothing about 1990. I'm illogical from your perspective perhaps, but I'm at least literate.