What day of week was the 15th May of year 12'037, has a grasp of Venus' phase?
Pleas familiarise yourself with: Doomsday rule (wiki).
Quest's boards:
Elm library to calculate: "Day of week from any date", with small sample App, to drive learning of this algorithm for any human being via Question-Answer-Solution Loop game. Idea and algorithm: https://youtu.be/714LTMNJy5M