Another week and another Infinity Stone in the spotlight. We've been going over the stones as Marvel 101's are doing the same and we've covered the Mind and Reality stones so far. The Time Stone or Gem is pretty straight forward in that it allows the user to control the past, present and future. More specifically it allows glimpses into future timelines, grants time travel, gives the ability to control someone's age and you can trap your enemies in an infinite time loop. All fun things. When combined with the other stones it allows the user to exist in all times at once. You'd think that would be kind of confusing. On Earth-616, its fallen into the hands of the usual suspects like Thor, Thanos, Tony Stark, Gamora, Adam Warlok, Nebula, Gardener, Loki, Mr. Fantastic, Namore, Maxam and Hardcase. It also ended up in the posession of Lockheed, Kitty Pryde's dragon.
In the MCU, we got our first look at the Time Stone in the recent film Marvel's Doctor Strange. The stone is inside the Eye of Agamotto and allows the user to alter time, an example we get to see when Strange takes a bitten apple back to it's whole form and then forward until it is rotten and then back again. He uses it to restore a missing page from the Book of Cagliostro and learn about Kaecilius and his plans with Dormammu. He also uses it at the end of the film to undo the destruction of Hong Kong, save Wu and then trap Dromammu in a timeloop… hence, "Dormammu, I've come to bargain." The Time Stone is still in the Eye of Agamotto and in the possession of Doctor Strange.
Here is the latest Marvel 101 showing a brief comic history on the Time Stone.