It was a string array first. ISO came long after the Gregorian calendar. And the months came from the Julian calendar.
If we go all the way back, one could say it was a mixed array of string and integer. September (7), October (8), November (9), and December (10) are linguistically ordinal names... but they’re all off by two since the deprecation of the Roman calendar.
If we go all the way back, one could say it was a mixed array of string and integer. September (7), October (8), November (9), and December (10) are linguistically ordinal names... but they’re all off by two since the deprecation of the Roman calendar.