"Forty, Counting Down" is a science fiction short story involving time travel, written by Harry Turtledove. It first appeared in the December 1999 issue of Asimov's. This same story is also told in the story "Twenty-One, Counting Up" but from the protagonist's younger perspective. It is available in the collection Counting Up, Counting Down. In 2000, "Forty, Counting Down" was nominated for the Hugo Award for Best Novella. Turtledove insists in the Counting book that the Justin Kloster Stories can be read in any order, and refuses to say which was written first.