void SetGMonth(BYTE month)
  Property Description  
    Argument month sets the Month part of the date. Jan = 1, Feb = 2 etc. (Valid Range = 1 to 12)  
    Description Populates this CDateTime as type gMonth  
    Remarks Throws: LtInvalidValueException thrown on parsing invalid values.
Throws: LtInvalidStateException thrown if this DateTimes current type is not either zeroYear or gMonthDay.