Simple pendulums were long the basis for accurate clocks. Time keeping in such pendulum clocks depend on the
period of the pendulum which in turn depends on the length of
the pendulum and the acceleration of gravity. Clearly a grandfather clock would be terribly slow on the moon but
adjustments must even be made if we transplant such a
device to the top of the Sears tower. According to Newton's
expression for the gravitational force we have (neglecting the correction due to the rotation of the earth about its own axis)
Thus the period of the pendulum at height h is
The clock will thus go slow by an amount
A day has 86400 seconds so the clock would loose
per day, which would be noticeable. Not to worry though since
a small adjustment to the effective length of the pendulum
could quickly fix this.