Your dates

This is the full challenge — find the weekday for a complete date — but you choose which dates come up.

Above the level picker you can narrow the deal in two ways, matching the two halves of the year calculation:

• Centuries — each century has its own anchor day, so limiting to one century lets you drill the rest of the algorithm without switching anchors (and picking several drills exactly that switching).
• Years within the century — the two-digit part the div-12/mod-12/div-4 arithmetic runs on. Set 84–99, say, and every date ends in ’84 or higher — the years with the heaviest mental math.

Your choice is saved on this device and every round draws from it. Same rules as the other games: 15 rounds, 3 lives, and higher levels give you less time.

New to the algorithm? Start with how the doomsday algorithm works and the earlier games on the roadmap.