From the Eagles song
In a new york minute everything can change
In a new york minute things can get pretty strange....
Kind of like instantly I suppose.
And here was I, thinking about the New York second. Which means pretty much the same thing, but has the formal definition of the amount of time between the light changing to green and the cabbie behind you honking. I can only presume that Mr Pratchett got that one from the New York Minute.