Te millennium celebrations are based upon what-ever the celebrators want them to be based upon, but a millennium is 1000 years (and has no bearing at to what the years are actually. Dublin celebrated it's millenium in the 1980's, Iceland celebrated it's millenium in 1966.
The year 2000 is an appropriate date to celebrate athe millenium IF your millenium started in 1 BC. Only those people locked into the Christian-focused concept of history are even paying attention to this whole thing (except for two other groups of people - those around the world with old computers and those who are cashing in on the Westerners (Euro/American/Australian mostly) who want a REALLY BIG PARTY)
Personally I don't give a damn what the excuse for a party is - let's just HAVE one!
pax yall