How is time warped by gravity?

Gravitational time dilation occurs because objects with a lot of mass create a strong gravitational field. The gravitational field is really a curving of space and time. The stronger the gravity, the more spacetime curves, and the slower time itself proceeds.

Can gravity bend time?

One proposed method of time travel is via wormholes. “We know that space can be bent. If space can be bent by, say, gravity, then spacetime can be bent,” Beacham said. ... If spacetime can be bent, Beacham continued, it's theoretically possible that time can be bent.