  From a thermodynamic point of view, all clocks are driven by irreversible
processes. Additionally, one can use oscillatory systems to temporally modulate
the thermodynamic flux towards equilibrium. Focusing on the most elementary
thermalization events, this modulation can be thought of as a temporal
probability concentration for these events. There are two fundamental factors
limiting the performance of clocks: On the one level, the inevitable drifts of
the oscillatory system, which are addressed by finding stable atomic or nuclear
transitions that lead to astounding precision of today's clocks. On the other
level, there is the intrinsically stochastic nature of the irreversible events
upon which the clock's operation is based. This becomes relevant when seeking
to maximize a clock's resolution at high accuracy, which is ultimately limited
by the number of such stochastic events per reference time unit. We address
this essential trade-off between clock accuracy and resolution, proving a
universal bound for all clocks whose elementary thermalization events are
memoryless.
