  For temporal magnitudes describing, in details, processes of particles
scattering for a long time at each necessity case a particular, ad hoc
reception were used. However the desirability of general approach basing on
concepts of quantum field theory and uniting two main problems, durations of
delay at scattering and of formation of arisen states, seems evident.
  We show that the Ward-Takahashi identity allows the defining of general
temporal function in the frame of QED, real part of which describes the
duration of delay of scattered particle on scatterer and imaginary part
describes the duration of formation ("dressing") of outgoing bare particle. The
functions of same form can be revealed in the known QED descriptions of
processes, i.e. they arise in the course of standard calculations, but are not
entered artificially. These functions submit to the operator of duration
determinable by the reciprocal analogue of the Schroedinger equation, operator
of which is canonically conjugated with Hamiltonian. Definition of temporal
functions leads to the developing of such kinetic theories: theory of optical
dispersion (with the decision of certain known paradoxes), theory of
multiphoton processes (definitions of their thresholds and saturations) and
theory of phase transitions (determination of general correlation radii and the
full system of critical indices). The determination of temporal functions
demonstrates also the instanton-type nature of tunneling processes, makes clear
sense of the adiabatic hypothesis of quantum theory and some renormalization
schemes. In an application to the problem of charge nullification they lead to
a restriction of allowable number of fermions of the theory.
