Originally Posted by Taibak

Gravity (which I ignored in my above examples, BTW), makes it far, far more complicated. It's not a simple linear relationship line Ohm's Law and the equation depends, in part, on the geometry, electric charge, and rotation of whatever massive object you're taking into consideration. For a spherical, non-rotating, electrically neutral object, at rest relative to an observer, the difference in time is given by:

dT= ((1 - 2GM/rc^2)^1/2) dt

where c is the speed of light, r is the distance from the object's center of mass, M is the object's mass, G is the universal gravitational constant, dT is the amount of time the an observer experiences at r, and dt is the amount of time the observer would experience without any influence from the massive object.

Hope that helps some.