Did you know that the year of "The end of the world" mentioned by the ghost mailbox is "3012"? Well, it is exactly when time baby would be regenerated. (Blendin once said: "Luckily, Time Baby isn’t dead...Exactly. It will take one thousand years for his molecules to reconstitute, and when they do, boy, is he gonna be cranky!") In fact, in "time traveler's pig", when dipper and mabel travel through time, when time baby destroys buildings, that's 3012!
Dipper learns that the end of the world is in 3012.
Blendin warns Dipper and Mabel that in one thousand years Time Baby will regenerate.
Time Baby is now regenerated and the world is finished.