Mathematics, why all this debate about when the decade ends? A decade ends every day?
The decade that began on January 1, 2001 ends December 31, 2010.
But a decade is a 10-year period. The decade that begain on January 2, 2000 ends today, January 1, 2010.
Similarly the decade that began on August 15, 2003 will end on August 14, 2013.
So there are thousands of correct definitions of the decade, the one you accept as your interpretation of the decade is your choice, but the other 3652 are just as correct, so people can't say your interpretation is wrong, because as long as yours lasts 10 years it's not.