There is running joke about general relativity and quantum mechanics being a demonstration of simulation hypothesis, i.e., floating point computations used to simulate our universe break down under very small and very large scales.
And mass slows down time because the load increases
Related to this, Second Life has a concept of time dilation which is the ratio of current simulator frame rate to ideal frame rate (30fps IIRC). As more avatars, scripts, and physically simulated objects were put in a simulator the time dilation increased.
Interesting, I first heard about this regarding EVE Online.