Anytime you move at a different speed, the definition of what time matches your current time shifts throughout the universe by an interval proportional to the distance—even if you’re just driving down the street, the time that matches “now” in your reference frame in a distant galaxy could change by years relative to what it was when you were stationary. Of course, you can’t actually see that happening, so the difference is just theoretical... as long as you can’t teleport to that galaxy faster than light.
But as soon as you have any kind of FTL travel, it’s trivially easy to go back in time by warping back and forth between two moving endpoints.