Time is measured on Earth with the decimal system. It takes ten years to make up a decade, not nine, and it takes one hundred years to make up a century, not 99 years. By the same token, 999 years do not a millennium make. A millennium is made up of 1000 years.
January 1, 1901 to December 31, 1910 was the first decade of the 20th Century. 1900 was the last year of the 19th Century, not the first year of the 20th Century, just the same way the year 2000 was the last year of the 20th Century and not the first year of the 21st Century.
It's all about multiples of ten. You have ten fingers. Count out a decade on them, then a century if you need to. If you need to count to 1000 on your fingers to understand how a millennium actually works then there's really no reason for you to read any further.
I would venture to guess that Hollywood played a major role in confusing people about the year 2000, making them throw out not only what they'd been taught in elementary school arithmetic and high school math, but their commonsense too. Movies about the new millennium were a dime a dozen in 1999 and in the year 2000, most of them dealing with the arrival or the departure of Satanic beings on planet Earth and a cape-and-sword battle for truth, the American way and the girl next door, because that's what sells tickets at the box office more than anything else. Romantic fantasy.
Another fantasy was the year 2000 being billed as the dreaded Y2K, a year that would fall flat on its face as soon as it arrived. When the year 2000 failed to bring with it the collapse of worldwide cyber technology, it confirmed the biggest computer hoax of all time and not the first year of some mysterious New World Order. But, thanks to Hollywood and its insatiable need to make tons of money off brainless people, the 21st Century and the new millennium came in on January 1, 2000.
For the couple dozen of us who knew better, however, the new millennium unceremoniously showed its face on January 1, 2001. And on January 1, 2011 the second decade of the 21st Century will just as quietly show its new face. But if you want any peace in your life, don't tell anyone.
