  The conundrum parameter-operator of time in quantum mechanics (QM), as well
as the time-energy uncertainty relation and the tunneling delay time, have
recently been addressed in attosecond optical ioniza- tion experiments. The
parameter status of time in the time dependent Schr\"odinger equation (TDSE) is
supported by the well-known Pauli's ob- jection as well as by its
interpretation as an emerging property of entangle- ment with a classical
environment. On the other hand, the introduction of a self-adjoint dynamical
time operator in Dirac's formulation of elec- tron's relativistic quantum
mechanics (RQM), yields an additional system observable that represents an
internal time. In the present paper the re- lation of this internal time with
the parametric (laboratory) time and its relevance to the tunneling
measurements in these experiments is examined within the standard framework of
RQM.
