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Very true! Thanks for the note.
You don't need to convert your switch cases to explicit boolean values. You already have them.
I thought this kata was calling for the coder to implement Zeller's congruence:
for the Julian calendar, given that the Gregorian calendar did not exist until 1582. My solution didn't work until I adapted it to calculate based on the Gregorian calendar, at which point everything passed.
Might want to explicitly state that. This is a coding exercise, not a history lesson, but it was a point of confusion for me. Thanks for the kata!