In 1905 Einstein derived, from his two postulates, the conclusion that "the clock moved from A to B lags behind the other which has remained at B":
http://www.fourmilab.ch/etexts/einstein/specrel/www/
Albert Einstein, ON THE ECTRODYNAMICS OF MOVING BODIES, 1905: "From this there ensues the following peculiar consequence. If at the points A and B of K there are stationary clocks which, viewed in the stationary system, are synchronous; and if the clock at A is moved with the velocity v along the line AB to B, then on its arrival at B the two clocks no longer synchronize, but the clock moved from A to B lags behind the other which has remained at B by tv^2/2c^2 (up to magnitudes of fourth and higher order), t being the time occupied in the journey from A to B."
Actually the conclusion
"The clock moved from A to B lags behind the other which has remained at B"
does not follow from Einstein's 1905 postulates - the argument is invalid. The following two conclusions, in contrast, VALIDLY follow from the postulates:
Conclusion 1: The clock moved from A to B lags behind the other which has remained at B, as judged from the stationary system.
Conclusion 2: The clock which has remained at B lags behind the clock moved from A to B, as judged from the moving system.
Conclusions 1 and 2, just because they are valid consequences of Einstein's 1905 false constant-speed-of-light postulate, entail contradiction (absurdity). Einstein hid the absurdity by deriving, fraudulently and invalidly of course, asymmetrical time dilation - the moving clock is slow, the stationary one is FAST. The famous "travel into the future" was a direct implication - science died and magic was born.
Pentcho Valev