There was no Gregorian year 1, 2, 3, 4, 5, 6, ..., or 1581, either. There is no contradiction in the calendar starting on a 1 but decades starting on a 0; either way the calendar actually started in the middle of a decade/century/millenium. True pedants should be insisting the decade starts on a 2, and centuries start on 82s!
There was no year zero. Thus, since a presumed January 1st, 1 AD, there have been 200.9 decades.
(And for the record, I posted that out of humor, not pedantry.)
There was no Gregorian year 1, 2, 3, 4, 5, 6, ..., or 1581, either. There is no contradiction in the calendar starting on a 1 but decades starting on a 0; either way the calendar actually started in the middle of a decade/century/millenium. True pedants should be insisting the decade starts on a 2, and centuries start on 82s!