Public Sub SetGYearMonth(ByVal iYear As Long, ByVal iMonth As Byte)
  Property Description  
    Argument iYear year sets the Year part of the date. (Valid Range = -9999 to 9999)  
    Argument iMonth month sets the Month part of the date. Jan = 1, Feb = 2 etc. (Valid Range = 1 to 12)  
    Description Populates this DateTime as type gYearMonth.  
    Remarks Throws: on parsing invalid values.
Throws: if this DateTimes current type is not either zeroYear or gMonth.