Relativistic propagators, the natural tools in field theory to describ
e the space-time development of a quantum system, are used to study co
rrelations and interferences present in the neutral kaon system due to
time-reversal violations. The method allows for a general wave-packet
treatment of the problem. While standard results are obtained for sin
gle K decays, quite different results are derived for the interference
phase in two kaon decays such as those at DA Phi NE.