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.
So, it's pretty easy to time travel, you just need a spaceship that can go really fast in a high gravity environment, lots of aliens are probably time traveling right now.
Gil Pérez, a 16th century Spanish soldier, claimed to have teleported from the Philippines to Mexico City.
He also claimed to be aware of the assassination of the governor of the Philippines and was thrown in prison until the assassination..