Back in spring 2020, I was wrapping up the distributed systems course I was teaching, and for the last lecture, decided to spend a little time poking at the question of who actually invented vector clocks. Most people who need something to cite for vector clocks cite Friedemann Mattern’s “Virtual Time and Global States of Distributed Systems”, dated 1989 (although the workshop at which it originally appeared apparently actually took place in 1988), and Colin Fidge’s “Timestamps in Message-Passing Systems That Preserve the Partial Ordering”, dated 1988.1 (The done thing is to cite both Fidge and Mattern, who apparently worked independently without knowledge of each other’s work on the topic, though Mattern does cite Fidge in the version of his paper dated 1989.) It can be hard to find authoritative versions of older papers online! I can’t find publisher editions of either the Mattern or Fidge vector clock papers. Instead, I’ve linked to the most auth