Of course time travel in a forward direction is well proven but the effect of gravitation still remains a kind of mystery (to me anyhow)
One Mark in another thread speaks of time travel with reference to the center of an explosion, intriguing.
Of course at that instant the concentration of matter might engender a local increase in gravitation which would indeed slow any clock capable of withstanding it but wouldn't the diff be very slight
….suggesting another q: If gravitation slows a clock, might a high pressure not also
....and how about the effect of acceleration, terrific I'd think near the very center