Last time at Jonbuddy's blog, he explained few things about this "time paradox" theory in last Saturday's "It's About Time episode. However, although he has explained few things about his theory, there were some people who didn't sort of understand what it meant. I do understand what he was trying to say, but just concluding this theory doesn't mean its exactly right. So, in my theory, I've thought of it as a "parallel world theory", where Twilight's time traveling was actually took place in a "same but different world". I'll explain it by using the pics I've created using the new Photoshop I just got last Friday.(Yeah baby, its back!!!)
In this world, there are actually countless various worlds with different time lines. Which mean, although they all take places in the same world, they're actually connected to different time lines from each other. We call this, a "parallel world", or an "alternate worlds".
In the beginning, the "Future Twilight", which we'll call this "Twilight A", tried to use a time traveling magic in order to go to her past by telling her past self for not to worry what's gonna happen in the future.
However, rather than going straight to "Past A", for a mysterious reason, a warp tunnel to the alternate time line suddenly opens, taking Twilight A from "Future/Present A" to "Past B".
After Twilight A arrived to Past B and confronted the "Past but Alternate Twilight", which we'll call her "Twilight B", the time limit of Twilight A's magic will cut off, and force her to return to Present A. Furthermore, since she came back from the different time line, time paradox, or changing history method, never occurred in her original world.
Then Twilight B does the same action like what Twilight A did back in her original world, and every events has went on from Past B to Future/Present B, just like how it was in World A.
Then Twilight B uses the time magic again, opening the another warp tunnel to the different time line, meeting with Twilight C, and doing the same actions like how other Twilights in the other worlds did.
Then this continues on, that Twilight C will go to Past D, and Twilight D goes to Past E...which means, these methods will continue on eternally as in a loop, which there will be no time paradox or history changes occurred in any worlds and time lines.
In conclusion, as in theory which may be fictional, time paradoxes or history changes does not occur or never exists, which this type of situation will repeat itself without having a will of changing the ways. And this type of theory is pretty much understandable, since this theory was pretty much used in most but some cartoons and comics, even mangas and animes as well. But, its up to your understandings. Its okay if you don't understand what I'm trying to say, because we can leave the answers alone as a mystery that'll never be solved. We'll just leave it up to everypony's imaginations.
By the way...did anybody felt sick for Spike eating ice cream for more than 24 hours?