now I hand fred an apple...how many now? 1 but by your reasoning, he has 2......
He has 1, because, it is only at this stage does he start counting.
Exactly... Fred doesn't say, when his hands are empty: "Oh look, I have zero apples in my hand!", does he?
Zero is a vacant number, in fact, and occupies a space in the mathematics table purely to add units of 10, 100, 1000 when 9,99, 9999, etc, have accrued.
So, by using that logic, the fact that a decade is 10 full years... not a moment less, we can count the 2000's as a decade as being over only when 2010 is concluded. This is calculation is reached purely by virtue of the mathematical fact that the first complete year of the decade hadn't elasped until 31 December 2000 at 12.00am. Prior to that point in time, 2000 qualified only as a collection of 11 months, plus 30 days 23 houra 59 minutes and 59 seconds.