How exactly does gravity affect time?

[robvalue]

The whole idea of time being relative is really hard for me to grasp. Even when I see the theory and the maths laid out, part of my brain still shouts, "Yeah, but bollocks!"

I've tried thinking more of time as a fourth dimension rather than a simple parameter. That has helped a bit.

I'm wondering if time is defined in terms of the rate of change of distance with respect to speed; rather than the more usual formulation. Does that make any sense.... or help?