There is a thing called the Twin Paradox used to illustrate relativity in time. Taryn and Karyn are twins. In 2002 Karyn stays home, but Taryn flies to Alpha Centauri and back at very nearly the speed of light, a voyage that takes eight years of Karyn's time, but only a few days of Taryn's time. So Karyn thinks its 2010, she's physically eight years older, but Taryn thinks it's still 2002 and her ship's clock agrees. She is physically only a few days older.
When Taryn steps off her spaceship and meets her twin, what year is it, 2002 or 2010? It doesn't matter! There is no time, there is only a universal eternal NOW, but clocks and heartbeats can beat slower or faster depending on their relative motion or position within a gravity well.
The implication is that even if you had a time machine, there would be no available destination. There is no future, nothing for a god or prophet to foresee, and the only past which endures exists in physical records (subject to redaction) and human memories. Even human memories are not stored as complete records but as simple highlights which can trigger the brain to recreate the past at will. That is why three different eyewitnesses can have five different testimonies. Politicians and religious authorities know, like Santayana did, that to repeat the mistakes of the past they must control the teaching of history.
Some believers will object that this limits God, who can “see the end from the beginning” according to the scriptures, but we do not ask God to do impossible things, like create a four-sided triangle or a billiard ball that is all black and all white. The future does not and cannot exist, so even God can be forgiven for not knowing it. And this, in turn, guarantees that our will is always free.