Page "General relativity" Paragraph 37

Assuming that the equivalence principle holds, gravity influences the passage of time.

Light sent down into a gravity well is blueshifted, whereas light sent in the opposite direction ( i. e., climbing out of the gravity well ) is redshifted ; collectively, these two effects are known as the gravitational frequency shift.

More generally, processes close to a massive body run more slowly when compared with processes taking place farther away ; this effect is known as gravitational time dilation.