[onraglanroad]

But they were right and you were wrong. Your mistake is in thinking that years are cardinal numbers when they're actually ordinal.

The current year counting was based on the same way years were counted in the past, so you had things like "the 10th year of Caesar's reign". So the year 1 A D. was the first year of Christ's reign.

The year 2000 was the 2000th year of Christ's reign so that's what is celebrated.

Alternatively, you don't really care about that and it's called Common Era now anyway, but in that case it's entirely arbitrary. So either way, calling 2001 the New Millennium is wrong!

[IIsi50MHz]

The first 10 years are 1 through 10. That is the first decade. Consequently, the next decade is years 11 through 20.

The first century is years 1 through 100. Therefore, the second century is years 201 through 300.

The first millenium is years 1 through 1000. Therefore, the second millenium is years 2001 through 3000.

There is no year zero.

[onraglanroad]

The first year of Christ's reign is the year 1.

The hundredth year of Christ's reign is the year 100.

The thousandth year of Christ's reign is 1000.

The two thousandth year of Christ's reign is 2000.

There is no year zero.