Illustrating the relativity of simultaneity
  We present a relativistic space-time diagram that displays in true magnitudes the readings (daytimes) of two inertial reference frames clocks. One reference frame is the rest frame for one clock. This diagram shows that two events simultaneous in one reference frames are not compulsory simultaneous in the other frame. This approach has a bi-dimensional character. 
Bernhard Rothenstein, Stefan Popescu, and George J. Spix