  The paper is intended to clarify operational meaning of mass and time
quantities as main characteristics of an atomic clock, which is considered a
quantum oscillator in association with the de Broglie wave concept. The
specification of the concept of clock in quantum terms reflects the idea of
relativistic mass and time complementarity, which is important for avoiding
ambiguity of such notions as ``time rate'', ``time record'', and ``elapsed
time'' under relativistic conditions. We used this approach in SRT Kinematics
to conduct a detailed analysis of the clock paradox; results are discussed. It
is also shown that in SRT Dynamics the proper mass must be acted by Minkowski
force, what results in a clock rate variation.
