Librivox M4B - Conquest Over Time by Michael Shaara

Pat Travis, a spacer renowned for his luck, is suddenly quite out of it. His job is to beat his competitors to sign newly-Contacted human races to commercial contracts...

But what can he do when he finds he's on a planet that consults astrology for literally every major decision - and he has arrived on one of the worst-aspected days in history?

Michael Shaara, later to write the Pulitzer-winning novel "The Killer Angels", wrote this story for Fantastic Universe in 1956. (Summary by Mark F. Smith)