> 2000 to 2010 is 11 years

This is obviously wrong by induction.

If 2000 to 2010 is 11 years, then:

2000 to 2009 would be length 10 years

...

2000 to 2001 would have length 2 years

and finally 2000 to 2000 would be a span lasting "1 year".

But any span with the same start and end point must have length zero, it's nonsensical to have a system without that property.

As for the spec, ISO 8601 defines a decade as a period of 10 years starting with a year divisible by 10 without a remainder.

Decade 1 is year(s) 10 through 19.

fsckboy 4 days ago | parent | next [-]

>any span with the same start and end point must have length zero

"a year" is not a point, it's a span. so is a decade.

>Decade 1 is year(s) 10 through 19

but the property you are trying to describe goes hand in hand with 0-based indexing, and thus we see that ISO Decade 0 is >sad tuba< 9 years long

	▲	eterm 3 days ago \| parent [-]
		It is actually 10 years long by how ISO 8601 defines a decade. Also it's worth noting here that ISO 8601 has a year zero, which equates to 1BC in historical terms.

1718627440 2 days ago | parent | prev [-]

> 2000 to 2000 would be a span lasting "1 year"

Yes it is?