Fixes "MMMM" and "MMM".

[nasyxx]

There is no need to -1 here.

calendar.month_name

An array that represents the months of the year in the current locale. This follows normal convention of January being month number 1, so it has a length of 13 and month_name[0] is the empty string.

calendar.month_abbr

An array that represents the abbreviated months of the year in the current locale. This follows normal convention of January being month number 1, so it has a length of 13 and month_abbr[0] is the empty string.

[Delgan]

Thanks a lot for the fix, it was a very unfortunate bug.