After "The Time of the Doctor", this seems very unclear. In "The Day of the Doctor", several references are made to the fact that by sealing Gallifrey in a pocket universe and changing the outcome of the Time War, the incarnations of the Doctor are changing history. Some of the indicative quotes are:
The Moment: It's history for them. All decided. They think their future is real. They don't know it's still up to you.
The Moment: They're you. They're what you become if you destroy Gallifrey. The man who regrets and the man who forgets.
Ten: You're not actually suggesting that we change our own personal history?
Ten: "This time, you don't have to do it alone."
Eleven: "This time, there's three of us."
Eleven: "Because the alternative is burning." Ten: "And I've seen that." Eleven: "And I never want to see it again."
However, the notion that time was actually changed seems to be contradicted by the events of "The Time of the Doctor", in which the Siege of Trenzalore is shown to be caused by the Time Lords, who are broadcasting the Question throughout the universe from within their own pocket dimension, which the Doctors put them into in "The Day of the Doctor." But since we saw a desolate, post-Siege Trenzalore with the Doctor's grave in "The Name of the Doctor", the Time Lords had to have already been saved in order for that version of the world to exist, which would mean that even then, the Doctor had been traveling in a timeline in which Gallifrey had been saved by his future (and past) selves.
This interpretation also has its merits, because shortly after the beginning of "The Day of the Doctor", the Eleventh Doctor sees a time fissure open up in the National Gallery and "almost" remembers it, as if he had been through it before (which, assuming that the whole thing is indeed a causal loop, would make sense, because he would have seen it from War's and Ten's perspectives). Additionally, we are not shown anything to suggest that this is the first time that the Moment has taken a stand against the Doctor's actions. Everything that the Moment does could reasonably be thought of as having happened in every past iteration of the event.
And then there is the "same screwdriver" gambit that the Doctors enact in the prison cell in 1562 - by scanning the cell door with the War Doctor's screwdriver, they can compress the time that it takes it to complete the calculations necessary for disintegrating the door due to the age of the Eleventh Doctor's screwdriver, which is implied to be a 400-years-older version of the War Doctor's. But logically, if it is a similar screwdriver from a different timeline, whatever the War Doctor does with his should not affect it.
So my question is, did the Doctor actually destroy Gallifrey in a previous timeline and rescue it in a new one, or do the events of "The Day of the Doctor" contain a circular loop that has happened and will happen every time?