  A number of human activities exhibit a bursty pattern, namely periods of very
high activity that are followed by rest periods. Records of these processes
generate time series of events whose inter-event times follow a probability
distribution that displays a fat tail. The grounds for such phenomenon are not
yet clearly understood. In the present work we use the freely available
Wikipedia editing records to unravel some features of this phenomenon. We show
that even though the probability to start editing is conditioned by the
circadian 24 hour cycle, the conditional probability for the time interval
between successive edits at a given time of the day is independent from the
latter. We confirm our findings with the activity of posting on the social
network Twitter. Our result suggests there is an intrinsic humankind scheduling
pattern: after overcoming the encumbrance to start an activity, there is a
robust distribution of new related actions, which does not depend on the time
of day.
