About slow time in gravitational field?

Interesting question. Of course a pendulum merely converts the potential energy (of position at the top of the swing) to kinetic energy (of velocity at the bottom of the swing) and each cycle marks an event. For the observer to observe less events than actually occurred there would have to be a time distortion. The pendulum obviously is not in a black hole (or it could not be observed at a distance). One thought is that if the observer approached the pendulum it would have to swing 'faster' to make up for the events that have been 'stored.' When there is a time distortion due to velocity (one twin approaches the speed of light and returns to earth younger than his twin) the distortion is permanent (as observed on identical accurate watches). Perhaps the pendulum sustains a time distortion (in local time neglecting the effect of gravity on its period) but the distortion is corrected as photons reach the distant observer. A person in a space ship traveling near the speed of light contracts in the direction of travel (becomes flattened) but is unaware of the contraction and any distortion of time.