types of anachronisms

Once upon a time, I came across two words. Both referred to specific types of anachronisms. One meant things that were ahead of their time, and the other meant things that were archaic or obsolete. I believe they both ended with “chronism”.

Any ideas?

It sounds like you might be thinking of metachronism (“An error committed in chronology by placing an event after its real time”) and prochronism (“The dating of an event before the time it happened; an antedating; – opposed to metachronism”). There’s also parachronism (“An error in chronology, by which the date of an event is set later than the time of its occurrence”), which seems pretty much synonymous with metachronism.

Indeed. Thank you!

Excellent answer, MEBuckner. I couldn’t (and, given the way things have been going lately almost certainly wouldn’t) have said it any better myself.

Well, that’s mostly just the way the 1913 Webster’s Revised Unabridged Dictionary said it. The “floating search” option is very nice.