360º view of the Perpetual Calendar
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...
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