I want to add a custom calendar to Windows 7's calendar type list, but I don't know how!

When you change regional settings (in "Region and Language" window, "Formats" tab, "Format:" Drop-Down list) to "Thai (Thailand) or Hebrew (Israel) or Arabic (Saudi Arabia)" for example, and then click on the "Additional settings" button, in the "Date" tab of the "Customize Format" window, the "Calendar type:" Drop-Down list appears that you can select one of those calendar types in the list, and then, all applications use that selected calendar.

I'd like to add a new calendar type to that list.

Another related question: How do I get this calendar date in Delphi? Delphi functions in the DateUtils unit do not get the localized Windows calendar.