[photochemsyn]

I think it all comes down to whether you're counting elements as the primary goal. However, months are poorly defined relative to something like an astronomical year or a standard day, so they're more like objects. That is to say, adding different months doesn't give you the same number of days as a result.

Hence, dealing with months is perhaps a bit more like indexing variable-sized objects, and for that purpose traditionally, the array-of-pointers approach uses zero-based pointer arithmetic, which is what the designers might have been thinking.

Really however, the months should probably be treated more like structs, with the number of days in that month being a data member. This would allow sanity checks, i.e. entering Feb 30 should raise an error, but not May 30.