method for calculating time, used in https://github.com/doug7410/punch-clock

gistfile1.rb

def total_time_on_job
  total = 0
  self.punches.each do |punch|
 
  if punch.punch_out
    punch_in_time = punch.created_at
    punch_out_time = punch.punch_out
    total_time = punch_out_time - punch_in_time
    total += total_time
  end
end