OpenBSD hackathons have been held at least once per year for ~17 years [1].<p>[1] <a href="http:&#x2F;&#x2F;www.openbsd.org&#x2F;hackathons.html" rel="nofollow">http:&#x2F;&#x2F;www.openbsd.org&#x2F;hackathons.html</a>