docs: def setDuration( self, duration ):
          """
          Changes the number of days that this item represents.  This will move
          the end date the appropriate number of days away from the start date.
          The duration is calculated as the 1 plus the number of days from start
          to end, so a duration of 1 will have the same start and end date.  The
          duration needs to be a value greater than 0.
          
          :param      duration | <int>
          """
          if ( duration <= 0 ):
              return
          
          self._dateEnd = self._dateStart.addDays(duration - 1)
          self.markForRebuild()