Steven J. Dick
U.S. Naval Observatory
Astronomical Applications Department
Massachusetts Avenue
Washington DC

You can read what he has to say at:

http://aa.usno.navy.mil/AA/faq/docs/millennium.html

Of course sanity is not the sole domain of the US military. The Royal Observatory Greenwich has this to say:

http://www.rog.nmm.ac.uk/leaflets/new_mill.html

Don't read it. And if you do read it, don't believe it. It's much more important what the marketing mavens want you to believe. All I want to know is, what does Ann Landers believe?