tor and tor-gencert disagree on what a month is
If I create a new authority-signing-key on June 1st at 00:00 with a life time of 5 months using tor-gencert, then the new authority signing certificate will expire November 1st at 00:00.
If I create a new identity signing key on June 1st at 00:00 with a life time of 5 months using tor, then the new identity signing cert will expire October 31st at 06:00.
Obviously this disagreement is suboptimal.