now class (to use the invaluable phraseology introduced by Bingley), this whole argument about centuries and millennia is sooo easy to resolve if you reduce it to (and think about) decades. to wit, what are the dates of the decade known as the "nineties"? 1990 to 1999, or 1991 to 2000? now, what do you think the years of the 20th century are (were) 1900 to 1999, or 1901 to 2000? QED, the lack of the year zero (0) or not (or naught) not withstanding.