  The aim of this article is to analyze the relation between the second law of
thermodynamics and the so-called arrow of time. For this purpose, a number of
different aspects in this arrow of time are distinguished, in particular those
of time-(a)symmetry and of (ir)reversibility. Next I review versions of the
second law in the work of Carnot, Clausius, Kelvin, Planck, Gibbs,
Carath\'eodory and Lieb and Yngvason, and investigate their connection with
these aspects of the arrow of time.
  It is shown that this connection varies a great deal along with these
formulations of the second law. According to the famous formulation by Planck,
the second law expresses the irreversibility of natural processes. But in many
other formulations irreversibility or even time-asymmetry plays no role.
  I therefore argue for the view that the second law has nothing to do with the
arrow of time.
  Key words: thermodynamics, second law, irreversibility, time-asymmetry, arrow
of time.
