Ramadan starts 10 March so the Saudi GP was scheduled 1 day earlier and F1 rules dictate 7 days between events so Bahrain had to move as well

https://www.skysports.com/f1/news/12433/13081415/why-are-the-opening-2024-f1-races-on-saturday-schedule-changes-for-bahrain-and-saudi-arabian-gps-explained