 
                 # Compute event.end as event.start + event.duration.
                 mDateRecurrentE = mDateRecurrentS.clone()
-                    .add 'seconds', mDateEventE.diff(mDateEventS, 'seconds')
+                    .add mDateEventE.diff(mDateEventS, 'seconds'), 'seconds'
                 fce = generator @, mDateRecurrentS, mDateRecurrentE
                 return fce
 

        if @endDateField
            @_toDateObject @get @endDateField
        else
            @getDateObject().add('m', 30)

    # Format a moment to the string format of the model.
    _formatMoment: (m) ->

            else if diff is -23
                diff = 1

            mDateRecurrentS.add diff, 'hour'

            return mDateRecurrentS

