The key isn't random just because it's an identity, as long as when the records for the date table were created in the correct "month" order. And no, it isn't dangerous.

Nice article. I already have a numbers table that I use regularly, maybe it's time for a dates table like this.

As for for Tom's comments concerning staying away from tables like this where you are worried about not have data for a given year. Relax. You could load this table through 2500 and it would still easily reside in memory.