On the positive side, it's straightforward and is void of cleverness (yes I've been doing Go, can you tell?).

I mean if I were to change that option string generator, I could make a numeric for loop from 1 to 12, left-pad a zero for the value, and lookup the month label from a label array or create a Date object and use its formatting options to output the label. I loop over an array of objects with a value and label. With ES6 I could do that with a .map() operation.

It's inelegant but it does what it says on the tin. Can't have an off-by-one error if you don't use loops or indices.