I thought about the date after I posted. It was 1978 or thereabouts. We actually had it on a PDP 11/45 running the prior version of UNIX that was, ISTR, Version III.
Mine was a PDP 11/34 running UNIX Version 7 in the basement of the Psych building at the University of Waterloo, from 1979 to 1983. Those were the days. Lots of fun and dot matrix printing, which is the only way I could actually study and debug my code.