360º view of the Perpetual Calendar













Comments

Post a Comment

Popular posts from this blog

Doomsday Timeline

by the doomsayers The Doomsday Algorithm was first introduced in 1973. Over the years, it has undergone many refinements and improvements. The ultimate goal is to make the algorithm easy to calculate mentally in addition to being easy to remember. Here is a timeline of important modifications to the Doomsday algorithm. Please email spectralfft at yahoo.com for corrections/suggestions to this timeline 1882: Christian Zeller devised the Zeller's congruence algorithm for determining the day of the week for any calendar date. This algorithm is not suitable for mental calculation but works well in computer software. 1887: Lewis Carroll published a perpetual calendar algorithm in the journal Nature with the title "To Find the Day of the Week for Any Given Date". Carroll's algorithm can be performed mentally. Lewis Carroll, himself, can calculate the day of the week in about 20 seconds. 1967: Martin Gardner published "Tricks of Lightning Calculators...
Read more

A Perpetual Calendar based on Lego™

Image
My desk calendar displaying October 2020 List of parts 31 Technic treads (Bricklink #57518) 2 Technic small wheel sprockets (Bricklink #57520) 12 gray 2x12 plates 12 2x4 plates 30 2x2 plate with bottom pin 15 gray 1x5 thin beams 92 white 2x2 tiles 2 axles 2 round 2x2 brick with grille  2 bent liftarms 2 L-shaped liftarms 3 1x3 thin beams 3 L-bracket 2x2  3 modified 1x2 x 2/3 brick with studs on side  3 2x2 plate with pin hole 3 gray 2x3 plates 3 2x4 plates 3 2x6 plates 6 1x2 jumper plates 3 2x2 plates 6 1x2 plates 4 regular-size bushing 2 straight axle connector 1 1x15 beam 5 1x5 beams 6 1x7 beams 4 1x13 beams 2 1x11 beams plus many miscellaneous peg connectors
Read more

Methods for Accelerating Conway's Doomsday Algorithm

Image
updated arXiv version of this document: http://arxiv.org/abs/1006.3913 and part 2 http://arxiv.org/abs/1010.0765 Abstract We propose a simplification of a key component in the Doomsday Algorithm for calculating the day-of-the-week of any given date. In particular, we propose to replace the calculation of the required term: floor(x/12) + x mod 12 + floor((x mod 12)/4) with 2 y + 3(y mod 2) + z + leap where x is an input two-digit year; y is the tens digit of x; z is the ones digit of x; leap is the number of leap years in the y decade less than or equal to x excluding the start of the decade; We argue that this simplification makes the algorithm simpler and easier to calculate mentally. Introduction The Doomsday rule is an algorithm for calculating the day of the week for any given calendar date. It was invented by John Horton Conway in 1982. It was designed to be simple enough that, with practice, one can do the calculation in his head without paper or penc...
Read more