The way it works is like this –
A decade is 10 years. Easy. 10 whole years. Anything less is 9-and-a-bit, and not a decade! 🙂
If we started dates again, we wouldn't start with zero, would we? We'd start with 'one' because that would be the first year, yes?
And so therefore we'd start at the first day, of the first month, in the first year – 01/01/01.
With me so far?
(Because if we count anything (Bikes, chickens, money, miles etc) the first unit counted is 'one' 🙂 )
So, with a decade being 10 years the 10 years are – 1,2,3,4,5,6,7,8,9 & 10
1 to 10 is ten units (Years) and if it's anything less than 10, it's 9 and a bit.
So a decade is from 1st Jan in the first year (the START of the year) to 31st Dec in the tenth year (The END of the year) Not the ninth!
And yes, we celebrated the ticking over the number 2000, not the start of a new Milennium. TJ is correct.
🙂
It's all to do with basic counting, nothing complicated.
But we get all excited by the ticking over of a big number, which is understandable I think 😀
Whereas 1900-1999 inclusive would make a perfectly valid century, as will 2000-2099
True in a way, but for that to work, we'd have had to had a century with 99 years in it. Which doesn't work. 🙂