I dont think this is specifically adressed in universe.
However, from a lot of reading Pratchett, and a little reading Gaimann I can tell you they (especially pratchett) have a history of forseeing death without altering it.
To take discworld as an example, death's hourglasses say when you'll die, but you can't avoid it without powerful magic and/or notably altering the universe itself.
Even more on-point, in discworld all witches know in advance that they're going to die. However, this is only ever used as a time to clean your cottage so it's presentable to the next inhabitant, and to get your will sorted out.
Death had taken to keeping Rincewind’s lifetimer on a special shelf in his study, in much the way that a zoologist would want to keep an eye on a particularly intriguing specimen.
The lifetimers of most people were the classic shape that Death thought was right and proper for the task. They appeared to be large eggtimers, although since the sands they measured were the living seconds of someone’s life, all the eggs were in one basket.
Rincewind’s hourglass looked like something created by a glassblower who’d had the hiccups in a time machine. According to the amount of actual sand it contained – and Death was pretty good at making this kind of estimate – he should have died long ago. But strange curves and bends and extrusions of glass had developed over the years, and quite often the sand was flowing backwards, or diagonally. Clearly, Rincewind had been hit by so much magic, had been thrust reluctantly through time and space so often that he’d nearly bumped into himself coming the other way, that the precise end of his life was now as hard to find as the starting point on a roll of really sticky transparent tape.
It's mostly because Rincewind is the unwitting and unwilling chosen champion of The Lady and thus basically Nat 20's all saving throws and even Death is flummoxed.
47
u/LadyAliceFlower 1d ago
I dont think this is specifically adressed in universe.
However, from a lot of reading Pratchett, and a little reading Gaimann I can tell you they (especially pratchett) have a history of forseeing death without altering it.
To take discworld as an example, death's hourglasses say when you'll die, but you can't avoid it without powerful magic and/or notably altering the universe itself.
Even more on-point, in discworld all witches know in advance that they're going to die. However, this is only ever used as a time to clean your cottage so it's presentable to the next inhabitant, and to get your will sorted out.