"Years of the Gregorian calendar, which is currently in use today, are counted from AD 1. Thus, the 1st century comprised the years AD 1 through AD 100. The second century began with AD 101 and continued through AD 200. By extrapolation we find that the 20th century comprises the years AD 1901-2000. Therefore, the 21st century will begin with 1 January 2001 and continue through 31 December 2100.

"Similarly, the 1st millennium comprised the years AD 1-1000. The 2nd millennium comprises the years AD 1001-2000. The 3rd millennium will begin with AD 2001 and continue through AD 3000."

U.S. Naval Observatory, Astronomical Applications Department

"A millennium is an interval of 1000 years and a century is an interval of 100 years. In the Gregorian Calendar, which we use, there is no year zero and the sequence of years near the start runs as follows;

..., 3BC, 2BC, 1BC, 1AD, 2AD, ...

Because there is no year zero, the first year of the calendar ends at the end of the year named 1AD. By a similar argument 100 years will only have elapsed at
the end of the year 100AD. Since 2000AD is the 2,000th year of the Christian calendar, it will be the last year of the Second Millennium. So the 3rd Millennium and the 21st Century will begin at the same moment, namely zero hours UTC (commonly known as GMT) on January 1st 2001."

Robin M Catchpole, Information Services Department of the Royal Greenwich Observatory

Obviously, Gene, you not only can't count, you can't read.