  In this paper it is found that the spin four-tensor $S^{ab}$ can be
decomposed into two 4-vectors, the usual ``space-space'' intrinsic angular
momentum $S^{a}$ and a new one, the ``time-space'' intrinsic angular momentum
$Z^{a}$, which are both equally well physical quantities. It is shown that an
electric dipole moment (EDM) of a fundamental particle, as a four-dimensional
geometric quantity, is determined by $Z^{a}$ and not, as generally accepted, by
the spin $\mathbf{S}$. Also it is proved that neither the $T$ inversion nor the
$P$ inversion are good symmetries in the 4D spacetime. In our geometric
approach only the world parity $W$, $% x^{a}\to -x^{a}$, is well-defined in the
4D spacetime. The consequences for elementary particle theories and experiments
that search for EDM are briefly discussed.
