It looks to me that the Windows system is always using the Gregorian Calendar.
And if you changed the Calendar type in Regional Settings; Windows will just CONVERT the Gregorian date to your specified date - wherever windows shows you the date.
But in the back of it will always stay the Gregorian date.
So when VBA will check the date, it will always get the Gregorian date. (unless you add your own methods to convert it.)
