MonthNames Property Returns 13 Months?!

What I love about the DateTimeFormatInfo class is that it allows you to get a list of day and month names in the language of the current culture. It took me aback the other day that MonthNames property returned an array of 13 strings, twelve of which were month names plus one empty entry.

Upon closer inspection you notice MSDN says,

In a 12-month calendar, the 13th element of the array is an empty string. […] Calendar objects accommodate calendars with 13 months.

Of the calendars, supported by .NET, the HebrewCalendar class may have 13 months:

The Hebrew calendar has 12 months during common years and 13 months during leap years.

That explains it. It would’ve been handy to just bind a list of months to a date picker, but… Internationalization has never been easy.