The main purpose of this paper is to show that if the student has understood special relativity with Einstein synchronized clocks knowing that the times tE and t'E which appear in the Lorentz transformations are times measured with such clocks, then the teacher can obtain the Lorentz transformations with non-Einstein-synchronized clocks simply by replacing tE and t'E with a relationship which relates them to the times measured on this new set of clocks. All the relativistic effects which are a consequence of the manner in which simultaneity is ensured, are interpreted as an attempt of an inertial observer to measure the proper length of a moving rod or the proper time of a moving rod.