OK, the fish are arriving and the nonsense will stop soon. This will be my last non-fishing specific comment of the season.
Saying that the millenium doesn't end until the end of the year 2000 presumes that Y2K is indeed the 2000th year since we started counting this way. "There was no year zero", is what sophists like Lassie Albino will say.
But there wasn't a Year 1, either. It wasn't until the 3rd century of what we now call the common era that we began to keep track of time relative to the birth of Christ. So, the first objection to the purists is that the starting clock was inaccurate -- how confident is anyone that when we started saying "it's 295 A.D." that it had been exactly 295 years since the event?
Secondly, the way we keep track of time and years has changed radically over the centuries. There used to be ten months until the Romans inserted two to honor their caesers (Julius and Augustus), thus shoving back the other months and making them misnamed (October, the eighth month, now comes tenth).
Even when we had settled on 12 months and 365 days, calendars had gotten seriously out of whack from the solar cycle. Eventually Pope Gregory got some mathameticians together and came up with leap years and everything else that would harmonize the written calendar with the solar calendar, so the solstices and equinoxes would fall on the same dates year after year.
Anti-papal England, however, wouldn't adopt the Gregorian calendar because it had a pope's name on it, so for about 300 years the English and Roman calendars moved out of alignment with each other. Even in the days of the US revolution they were on different calendars. Depending on which source you read, you can get dates for George Washington's birth that are 12 or 13 years apart.
Well, now we're all on Gregory's time, but we didn't get here in one thousand nine hundred and nintey nine discreet intervals from a point in time when the historical Jesus was born.
So the millenium question is a matter of symbolism. And what is symbolic is that the odometer rolls over on 13/31 of this year. This is the last year of the millenium. Case closed.