Dear Rabbi, Some sources say that the 24 priestly courses would just repeat after every 24 weeks. Other sources say that they started at the first Shabbat after Pesach and Sukkot (2x a year) If that were the case, what would happen in a leap year (where there are 4 additional weeks)? Thank you, Shalom, Gerhard

The Talmud (Erchin 11b; Y’rushalmi Shkalim 5, 3) and most commentaries and halachic codifiers state simply that the order of the 24 kohanic families would continuously repeat itself, with no mention of specific dates, and that solves your question of the leap year. As you mentioned, only the second and minority opinion (Rabbenu Chananel, Ravya) would be faced with this problem, and they don’t deal with it. I saw a modern day opinion conjecture that they probably did a lottery among the families to see who would serve 3 times that year, but that’s just speculation.