Larry, we're dealing with perception, not items. The basis for claiming that the new millennium doesn't begin until 1/1/2001 is based on the same perception of the passage of time by humans, made before there were clocks or accurate instruments to measure time passage. Perhaps they were off a year, perhaps they weren't. When there are calenders that don't reflect this date as a changing of a year at all, Jewish and Chinese come to mind, it all becomes a human created event.

A millennial calender is a bit more flexible than my making a doctor's appointment for a specific time during a day.

The 1900's will end tonight. The 2000's will start tonight. Call it the beginning of the new millennium, call it the beginning of the end of the last, it really doesn't matter, because it can be seen as both. It is arbitrary Larry.

Best to you, and Happy 2000!
Bob