As on Earth, the period of rotation of Mars (the length of its day) is
slowing down. However, this effect is three orders of magnitude
smaller than on Earth because the gravitational effect of Phobos is
negligible and the effect is mainly due to the Sun. On Earth, the
gravitational influence of the Moon has a much greater effect.
Eventually, in the far future, the length of a day on Earth will equal
and then exceed the length of a day on Mars.
Jupiter is very gradually slowing down due to the tidal drag produced
by the Galilean satellites. Also, the same tidal forces are changing
the orbits of the moons, very slowly forcing them farther from