Night Shift and Sunrise/Sunset

Using an M2 MBA, running 13.4.1. Night Shift is set to turn on and off automatically at sunrise and sunset. But it seems to assume I am much closer to the pole than I really am! For example, sunrise today was at 5.37am, but Night Shift changed at 9.20am. I have the correct time zone selected (though that should make no difference as it changes with longitude, not latitude), the correct nearest city, and time zone is set automatically by my location. The time is also set correctly by an Apple server.
What’s up with this?