system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do planets bend time?
gpt
Gravity, as far as we know, is caused by distortions in spacetime caused by mass. Since it's a distortion of spacetime it impacts both: space...which is why things are "pulled" towards planets, and time...clocks run slower near big masses.

There's nothing special about planets in this respect, it happens with all masses, but planets are the largest masses except stars and black holes so it's more pronounced near them.

\*Technically\*, just moving your watch near a stack of free weights causes it to move a little slower, but it's such a small effect that you can't measure it.

On the other hand, GPS satellites have to correct their clocks for the distortion caused by being in earth's gravity well (and for the distortion caused by how fast they're going).