Jukka K. Korpela writes:

> The point is that year numbers aren't really "numbers" in a normal
> sense, any more than car plate numbers, credit card numbers, product
> numbers, or social security numbers are. Surely they can be regarded
> as numbers, but so can car plate numbers and the others.

Except that years do actually form a sequence, and it's possible to
perform maths on them; for instances, subtracting one year from another
yields a duration[*1], which is a meaningful quantity, whereas
subtracting a couple of credit card numbers is completely useless.

[*1] Yes, there are exceptions. But there are still many situations
where this is useful, because of the context, such as the range of
possible years and the location.


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