My apologies for the quality of the scanned image to the right, with those extra smudges across the lower half; it's what I had. I've never seen an undamaged copy of After Hours #17.
As for the story's origins, one day I sat down at the keyboard and wrote the opening scene, with the pentagram in a fancy office, as a sort of warm-up exercise. I do those sometimes. Sometimes they take off, sometimes they don't.
This one wanted to take off, but it was pretty wobbly. I didn't really have a story, and sort of built it up as I went along. I was maybe halfway through before I realized how it was going to end, with something other than the sun rising.
I didn't think it was a terribly good story, and I was trying to decide where to send it when After Hours cropped up looking for fiction. Since I wasn't optimistic about selling it to a major market like F&SF, I sent it to them, and they bought it, and it appeared in #17, the Winter 1993 issue. (My old bibliography says 1995. It's wrong.)
I don't think it's ever been reprinted except in my collection, Hazmat & Other Toxic Stories.
That's it; here's your list of handy exits: