"The earth is degenerating these days. Bribery and corruption abound. Children no longer mind parents…and it is evident that the end of the world is approaching fast."—Assyrian Tablet engraved in 2800 B.C.
I found this in Neil Degrasse Tyson's essay "Paths to Discovery" which appears in the 1998 book "The Columbia History of the 20th Century"
While Googling on this a few weeks ago, I found an exceedingly exhaustive analysis of the quote somewhere on the Internet (props if you can find the link, I lost it) offered by a gaggle of Assyriologists. Some of them seemed to be very down on the authenticity, as the citation trail goes dead in the 1920s. The only reason it was traced back that far, though, is because Google Books happened to have scanned that book in. Clearly this is an issue where "people on the Internet can only tell you about things that are on the Internet." Another member of the group was optimistic about doomsday predictions on old, possibly as-yet untranslated tablets.
So my question really should be: what is the oldest verifiable doomsday prediction that we know about? Preferably one that puts a time limit on doomsday, like "next tuesday."