What is difference between MonthGenitiveNames and MonthNames? Why there is blank as month?

Question

I'm confused about MonthGenitiveNames and MonthNames. There are month names as values of both, so what is the difference between MonthGenitiveNames and MonthNames.

Also why is there "blank" for a month? If you look at values of both, there are blank values. What is the reason for the blank in Month names?

Answer 1

Genitive names exist because some languages use a different case of nouns to express dates (genitive instead of nominative).

E.g. in Polish nominative for January is "styczeń" but to express a date 2 January you need to use genitive "2 stycznia".

Answer 2

Michael Kaplan has written a bunch about genetive (see http://www.siao2.com/2010/09/09/10059644.aspx and http://www.siao2.com/2012/01/05/10253370.aspx) so I won't rehash that. In short MonthNames are used in contexts where there is no day and GenitiveMonthNames are used in contexts where there is a day. The actual case may or may not be Genitive (it is so named because the first cases where this was important to distinguish did have a genitive case distinction).

In addition to being used for the Gregorian calendar, the MonthNames and GenitiveMonthNames properties are used for calendars other than Gregorian. When such a calendar system has 13 months, there will not be a blank for the 13th month. It will always be blank for Gregorian since there is no 13th month in the Gregorian system.