Hello mph. May I call you Miles?

I suspect that "prepone" is a jocular construct akin to the modern use of "couth". Google shows 2,730 hits, but they are mostly non-English sites or apparently the name of a hurtler. Still, there are plenty of instances of "prepone" as you have posited it, and I've used it myself, so it must be a goodly word .

Here is a link to a discussion of prepone when used in the contra-postpone sense: http://theatlantic.com/unbound/fugitives/moveitup.htm

Interestingly, there is an American Sign Language sign for this concept, and the New Oxford Dictionary of English lists it. Also interestingly, I see that our own tsuwm participated in that discussion.