  Time dilation is a difference in measured time between two clocks that either
move with different velocities or experience different gravitational
potentials. Both of these effects stem from the theory of relativity and are
usually associated with classically defined trajectories, characterized by
position, momentum, and acceleration. However, when spatial degrees of freedom
are treated in a quantum way and a clock is allowed to be in a coherent
superposition of either two momenta or two heights, additional quantum
corrections to classical time dilation appear, called kinematic and
gravitational quantum time dilations, respectively. We show that similarly to
its classical counterpart, kinematic quantum time dilation is universal for any
clock mechanism, while gravitational quantum time dilation is not. We also show
that although both of these effects reduce to incoherent averaging of different
classical time dilation contributions, there exists an additional quantum time
dilation effect that has no classical analog and can be extracted from
higher-order corrections to the system's Hamiltonian.
