Methods for Accelerating Conway's Doomsday Algorithm (part 2) · HackerPapers discussions

Methods for Accelerating Conway's Doomsday Algorithm (part 2) — mentioned by phpdave11

Thu, 20 Aug 2026 12:59:46 GMT

For figuring the doomsday of a particular year, you can use the Odd+11 rule. Let X be the last two digits of a year. If X is odd, add 11. Divide X by 2. If X is odd, add 11. Let Y = 7 − (X mod 7). Count forward Y days from that century's anchor day to get the year's doomsday. https://arxiv.org/pdf/1010.0765

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Methods for Accelerating Conway's Doomsday Algorithm (part 2) — mentioned by bumbledraven

Fri, 24 May 2024 13:50:43 GMT

Carroll's algorithm has evolved over the years. The First Sunday Doomsday Algorithm (https://firstsundaydoomsday.blogspot.com/2009/12/quick-start...) includes all the improvements published as of 2023, including Fong & Walters' nifty "odd+11" rule for calculating the year code (https://arxiv.org/abs/1010.0765).

Paper and discussion history. A mention is not an endorsement.