der Jour fixe — from French, a fixed day. Duden defines it as a meeting of a fixed group of people that takes place regularly, often on a set weekday. Its spelling note gives unser Jour fixe jeden Dienstagabend, our jour fixe every Tuesday evening. Its usage example is die Mitglieder haben sich schon über zu viele Jours fixes beschwert, the members have already complained about too many jours fixes.
turnusmäßig — as the rotation says. Duden defines der Turnus as a recurrence or order fixed in advance.