  We find a quantum mechanical formulation of proper time for spin 1/2
particles within the framework of the Dirac theory. It is shown that an
operator corresponds to the rate of the proper time and that the operator
contains terms which oscillate with a very high frequency. We deduce, as an
effect of these terms, the existence of an interference between the magnetic
field and the rate of proper time. There is a possibility that the conclusion
derived in this letter has some implications for astrophysics.
