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The Perpetual Calendar
(Marais Formula)

On this web site you will find how to calculate (in your head) the day of the week of any given date, in any century.

It has been the endeavour of scholars for centuries to devise a simple formula for calculating a perpetual calendar.
The Marais Formula was coined and developed by a South African, Etienne A. Marais, in Johannesburg in 1991 and simplifies the calculation of a perpetual calendar. It utilizes a calendar key that makes it possible for a person with basic mathematical skills to do seemingly intricate mental calculations and produce astounding answers. By reading through this web site and practising the methods you will soon be able to do the whole calculation within a few seconds, in your head. 

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Copyright ZAbra December 2008