Paul Schlyter <pausch@saaf.se>

There is a difference of opinion.  Steve Willner writes:

Big "end of millennium" parties were held on 1999-12-31.  The
psychological significance of changing the first digit in the year
must not be discounted.  (Preceeding these parties were the big
headaches that occurred as everybody rushed to ensure---appropriately
enough---that the date code in everybody's computer did not break on
the next day.)  However, the third millennium A.D. in fact begins on
2001-01-01; there was no year zero, and thus an interval of 2000 years
from the arbitrary beginning of "A.D." dates will not have elapsed
until then.

More details may be found in an article by Ruth Freitag in the 1995
March newsletter of the American Astronomical Society.  I am seeking
permission to include the article in the FAQ.

A view to the contrary is expressed by Paul Schlyter <pausch@saaf.se>:

On 2000 January 1 of course!  Some people argue that it should be 2001
January 1 just because Roman Numerals lacks a symbol for zero, but I
find that irrelevant, because:

   1. Our year count wasn't introduced until A.D. 525---thus the people
      who lived at A.D. 1 were completely unaware that we label that
      year "A.D. 1."

   2. No real known event occurred at either 1 B.C. or A.D. 1---Jesus
      was born some 6--7 years earlier.  Thus the new millennium
      should _really_ have been celebrated already, at least of we
      want to celebrate 2000 years since the event that supposedly
      started our way of counting years.... 

(Yes, the Julian calendar _was_ around at 1 B.C. and 1 A.D., but at that
time the years was counted since the "foundation of Rome.")

Interested readers may also want to check the Web sites of The Royal
Observatory Greenwich <URL:http://www.rog.nmm.ac.uk/> and the US Naval
Observatory <URL:http://www.usno.navy.mil/>.