So in my third scenario for my current campaign, I had my players run through a tower which ultimately revealed to be run by a future version of one of the characters who then promptly died (the NPC not the PC). Beyond the fact that I now have to incorporate temporal problems and plot points within my world, I created a really nice puzzle on the spot.

It's a 30ft cubed room where all sides emit a bright white light.  There is zero gravity throughout the whole room and the closer you go towards a wall, the slower time moves at an exponential rate. About 3 yards away from all walls, the 'exponential time slow' is slowing down time to an infinite rate, meaning that anything that's within the yard doesn't move at all. EX. if an arrow is shot from the exact center of the room, the arrow gets an arrow's length into the infinite yards and the character who shot the arrow moves backward due to inertia. 

The reason why the arrow makes it a certain distance is because of how beyond the infinite yards, the shaft of the arrow still moves. This forces the arrow to warp the infinite yards until the entire arrow is completely within it, then it stops because there is no external part of the arrow acting on it. The solution to the room is to have one of the players to push a pole or something longer than 9 yards through the entire length while being outside the infinite yards area. This warps the infinite yards to a point where the top of the area touches the bottom, breaking the spell that causes this slowing time effect. 

While a fairly simple solution, it took my players about 40-50 minutes to figure it out and it was completely by chance. If someone tries to teleport onto one of the walls, they just disappear from the game until someone solves the room as they teleported into a space where time continuously slows down.

I don't know how to draw this out on a map, but if someone can understand this: imagine a square with a circular gradient inside. The circular gradient is white in the center and greys out towards the walls. The gradient represents the speed that time moves that and the greyest area would be the infinite yards. The rate that time would slow at is an exponential graph. While the solution is if a rod forced its way through a plane, kinda like a space-time geometry diagram.

Overall if you can understand this, I recommend using this with players that are heavy into theoretical science and all that. Mine were and they loved it.

If you have any other ideas for time travel/time-based puzzles, post below I guess.

For a passageway: The other end of the hall seems 30 ft away, but for each step you take, the hall be comes three times as long. The players must walk backwards towards the end of the hallway.