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. Smylers -- http://twitter.com/Smylers2