It really is significant that the year rolls over, and not just because of the
Y2K problem. Do people wait until their odometer gets to 100,006.7 to get
excited about that event, just because the car had 6.7 miles on it when they
drove it off the lot? (Not that very many keep their cars that long these
days, but the point's still valid.)
Why then should we wait until the unlikely-looking date of January 1, 2001 to
declare that we've reached a huge mark in human history? The "cost" is that
the first millennium AD would be only 999 years, and even that's somewhat
specious. The folks in what we call AD 1 didn't know the year by that name.
Why should we worry about them, or Pope Gregory and his friends? Apparently,
they only knew FORTRAN 1582, which would explain the 1-bias. Besides, from
what I've heard, the Gregorians got the birth of Christ wrong anyway, perhaps
by a couple of years.
The point is that the year-date is a convention, not a mathematical certainty,
so why do we need to perpetuate this cumbersome silliness?
The one dichotomy we can't avoid, to my mind, is the names of the centuries.
This is the 20th century, and to try to call it the 19th because it starts with
19 would make talking about history impossible, for several generations. But I
still think that having "the 1900s" be different by one year from "the 20th
century" is a useless distinction.
Sorry, I didn't have time to make this shorter.
Who actually spent his entire first year at the age of 0.