Retrieves the calendar identifier for the current month calendar control.
A calendar identifier denotes a region-specific calendar, such as the Gregorian (localized), Japanese, or Hijri calendars. Your application can use a calendar identifier that has various language support functions.
This method sends the MCM_GETCALID message, which is described in the Windows SDK.
This control is supported in Windows Vista and later.
Additional requirements for this method are described in Build Requirements for Windows Vista Common Controls.