I suppose it's academic, but those of us who talk about Y2K to such an extent should know "all about it", it would seem. So it behooves us to get the 3rd millennium start date right -- it's January 1, 2001, not 1-1-2000. The year 2000 is the last year of the 20th century, and the last year of the 2nd millennium A.D. Upon this the U.S. Naval Observatory, the Royal Greenwich Observatory, and the Library of Congress all agree, as well as pretty much anyone who knows calendar science and history. The same type of "which year" argument raged in 1800-01 and 1900-01, but not many are around who remember that. :)

The thing that people forget is that the present era (A.D.) did not start with the year zero. There was no year zero. The year directly following 1 B.C. was A.D. 1. So the first two millennia A.D. must logically run up through the year 2000. Two millennia equal 2000 years, after all. Jan. 1, 2001 starts the 3rd millennium.

Here's a pretty humorous rant from the Times of London, Dec. 26, 1799; funny by virtue of its Don Rickles tone (but the logic is sound, and applies to our turn of century and millennium as well):

"We have uniformly rejected all letters, and declined all discussion upon the question of when the present century ends? as it is one of the most absurd that can engage the public attention, and we are astonished to find it has been the subject of so much dispute, since it appears to be perfectly plain. The present century will not terminate till January 1, 1801, unless it can be made out that 99 are 100. Eighteen centuries are 1800 years, then how can 18 centuries be completed till the year 1800 has expired? What is the meaning of a century, but a clear distinct series of 100 years? How can 100 be completed by 99? ... We shall not pursue this question further, nor should we now have said so much upon it, had not several applications been made for our opinion. It is a silly, childish discussion, and only exposes the want of brains of those who maintain a contrary opinion to that we have stated ..."

Links:

U.S. Naval Observatory

Royal Greenwich Observatory

Library of Congress

-- John Howard (pcdir@prodigy.net), September 13, 1998

Answers

You are correct from a "technical" viewpoint, but not from a "practical" viewpoint. The popular viewpoint is that the year 2000 starts a new millennium. No one, except a few specialists, cares whether the first millennium had 999 or 1000 years.

Of course the important point for computer programs is that the year 2000 does not have a "19" prefix, thus breaking all computer program code that expects all years to begin with "19."

-- Charles Moorehead (cmooreh890@aol.com), September 14, 1998.

The confusion stems from a series of mistakes made by a 6th century monk named Dennis the Short, who constructed a chronology for Pope Saint John I. He got the season wrong (most scholars believe Christ was born in the Spring), the year wrong (Christ could not have been born after what is now calculated as 4 BC, and probably a year or two before this), and he forgot about the year 0 (what programmers call the off-by-one bug). As a result, the first instant of neither 2000 and 2001 is exactly 2000 years from anything notable - both are arbitrary. As a result, your belief as to which starts the millenium depends on personal preference. Should we adopt the common sense attitude that when all the year digits change at once, this is the important moment? Or should we cling to the off-by-one bug (while conveniently ignoring all of Dennis' other mistakes) and pick the highly unintuitive option that the important change comes a year later? Historically, common people have recognized that what's important is when all the digits change, while the 001 folks have been systematically mis-educated, and treasure their training above their common sense. The hilarious editorial in the Times of London makes complete sense if you celebrated your first birthday the day you were born, but collapses completely if you had to wait a year to become a year old. Training can be strong indeed. Of course, it's true that the computers don't care about Dennis the Short - they will make it all too clear when the millenium really changes, regardless of the arbitrary system you may choose.

-- Flint (flintc@mindspring.com), September 14, 1998.