def +( other_program )
      raise ArgumentError if @program.class != other_program.class

      additional_duration = other_program.duration + 1

      program.duration    += additional_duration
      occurrence.duration += additional_duration
      occurrence.end_time += additional_duration

      self
    end
def +( other_program )
      raise ArgumentError if @program.class != other_program.class

      additional_duration = other_program.duration + 1

      program.duration    += additional_duration
      occurrence.duration += additional_duration
      occurrence.end_time += additional_duration

      self
    end
Extends this scheduled program with another program of the same type.