ROUND((61 + COS(3 * month - 22.5)) / 2) Admittedly rounding is still cheating but it allows compacter solutions than being spot-on every time. Handling Februar

ROUND((61 + COS(3 * month - 22.5)) / 2) Admittedly rounding is still cheating but it allows compacter solutions than being spot-on every time. Handling February is left as an exercise for the reader.