When a child is born, that child ends its first decade of life on the last day of its 10th year. All the current "___ of the decade" lists are confusing digits with decades.
The year 2000 was the last year of the last decade of the 20th century. There was no "year zero"; therefore, the first decade comprised the years 1 through (and including) 10. The second decade was years 11 through 20, etc.
The year 2010 will be the last year of the first decade of the 21st century. (Yes, the new millennium did not begin until Jan. 1, 2001. If you celebrated it on Jan. 1, 2000, you were a year early. Go back to the year 1 and count by tens to prove this to yourself.
