  A communication scenario is described involving a series of events triggered
by a transmitter and observed by a receiver experiencing relativistic time
dilation. The message selected by the transmitter is assumed to be encoded in
the events' timings and is required to be perfectly recovered by the receiver,
regardless of the difference in clock rates in the two frames of reference. It
is shown that the largest proportion of the space of all $ k $-event signals
that can be selected as a code ensuring error-free information transfer in this
setting equals $ \zeta(k)^{-1} $, where $ \zeta $ is the Riemann zeta function.
