We don't want to worry anybody, but the world seems to be slowing down. The rotation of our planet on its axis is definitely and measurably reducing in speed and may one day stop completely.
The good news, though, is it's going to take a while. At a rate of around 17 milliseconds per century - providing of course that the rate of slow down doesn't increase - we won't see an Earth day go from 24 hours to 25 for approximately two billion years. The slowing effect can mostly be blamed on the Moon - the impact of our satellite's gravity on our oceans creates tides, which gently drag back against the turn of the Earth on its rotation, slowing it down by an infinitesimally tiny amount on each spin.