Answer:
because year 1 to 99 was the first, so it still counts as a century .(by the way, if you don't know, a century is 100 years.) take out the last 2 digits in the year you're in and add 1, and that's what century you're in. for example, the year now is 2010. take away the 10. you get 20,+1=21. this puts us in the 21st century.