  We present a derivation of the structure and dynamics of a ticking clock by
showing that for finite systems a single natural principle serves to
distinguish what we understand as ticking clocks from time-keeping systems in
general. As a result we recover the bipartite structure of such a clock: that
the information about ticks is a classical degree of freedom. We describe the
most general form of the dynamics of such a clock, and discuss the additional
simplifications to go from a general ticking clock to models encountered in
literature. The resultant framework encompasses various recent research results
despite their apparent differences. Finally, we introduce the information
theory of ticking clocks, distinguishing their abstract information content and
the actually accessible information.
