Recently, Maya Reynolds did an excellent post on the appropriate use of prologues and backstory. In her analysis, prologues are often mistakes because they deal solely with backstory -- stuff that is history of the story, but that's not changing or moving. A prologue is usually only useful if it is an active (if preliminary) part of the story.
I personally don' t do prologues--I haven't come up with a story yet where one has seemed necessary--but Maya's description of the prologue really intrigued me. She compared the events of the prologue to a "precipitating event," like a trigger in the crisis counseling she's done. In crisis counseling, precipitating events usually happen six weeks in advance of someone calling a crisis hotline.
So this week I went back and looked at the stuff I'm working on right now, and sure enough, there they were, the precipitating events. In The Book, the story starts approximately six weeks after the main character gets busted by her parents for doing something dangerous. In the other current project, the main character is keeping a secret that started about six weeks before the book started.
That's not to say that all of my stories have precipitating events--the TRP, for example, starts almost at the very moment of the precipitating event--but it's interesting to see that the six week rule of precipitating events has found its way into my fiction.
I wonder how Maya's advice would work for people who do write prologues--does the six week rule apply? Is that the stuff that's being covered in your prologues? Or is the stuff that typically goes into prologues not precipitating events, but actually backstory, stuff that's over? Most of the ones that I recall reading have been backstory prologues, but I'm thinking about going to look at my book shelves to check that.