ForehandRF
Legend
Well, tbh we entered the 21 st century in 2001, not in 2000.In some sciences, like meteorology for example, they also consider decades starting with 1 and there are many other examples.Decade starts at 2011 and finishes at 2020. 1 to 10, 11 to 20, 21 to 30, etc are decades. Year 2000 was the last year of 90s and second millennium. Or to make it simple for you. When you're born, it takes a year to your first birthday, from 0 to 1. There are another 9 birthdays to your 10th birthday, i.e. total 10 bdays in your first decade of life, 1 to 10.