def elapsed_time(start_time, finish_time)
      duration  = finish_time.to_i - start_time.to_i
      hours     = duration / 3600
      remainder = duration - (hours * 3600)
      minutes   = remainder / 60
      seconds   = remainder - (minutes * 60)
      sprintf "%02d:%02d:%02d", hours, minutes, seconds
    end
def elapsed_time(start_time, finish_time)
      duration  = finish_time.to_i - start_time.to_i
      hours     = duration / 3600
      remainder = duration - (hours * 3600)
      minutes   = remainder / 60
      seconds   = remainder - (minutes * 60)
      sprintf "%02d:%02d:%02d", hours, minutes, seconds
    end
Returns a string representing the elapsed time in HH:MM:SS.