Contrary to apparent popular belief, the 3rd Millennium does not start on January 1st, 2000.

 

Think about it.. 
 
 

The first decade started at year 1, and lasted through year 10, and the second decade started at year 11. 

Likewise, the first century started at year 1, and lasted through year 100, and the second century started at year 101. 

Following this same logic, it's easy to see that the date spans of the first three millenniums are as follows: 
 

First Millennium Years 1 - 1000
Second Millennium Years 1001 - 2000
Third Millennium Years 2001 - 3000
Need proof?   Just ask the United States Naval Observatory , the official date and time keeper for the United States. They agree that everyone is starting their Millennium bashes a year too early. Even the Royal Greenwich Observatory agrees...