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Easter_Sunday ( TheYear )

Calculate gregorian easter sunday method by Gauss

  Average rating: 4.8 (26 votes) Log in to vote

Menno van Beek - Show more from this author Van Beek Zakelijke Software https://www.vbzs.nl

  Function definition: (Copy & paste into FileMaker's Edit Custom Function window)

Let ([ Y = TheYear ; G = Mod( Y ; 19 ) + 1 ; //golden number C = Left( Right( "0000" & Y ; 4 ) ; 2 ) + 1 ; //century L = Truncate( 3 * C / 4 ; 0 ) - 12 ; //leapyear correction M = Truncate( ( 8 * C + 5 ) / 25 ; 0 ) - 5 ; //moon correction S = Truncate( Y * 5 / 4 ; 0 ) - ( L + 10 ) ; //sunday E1 = Mod( 11 * G + 20 + M - L ; 30 ) ; E = Case( E1 = 24 or E1 = 25 and G > 11 ; E1 + 1 ; E1 ) ; //Epacta (age of the moon on january 1st) N = 44 - E + Case( 44 - E < 21 ; 30 ; 0 ) ; //Full moon P = ( N + 7 ) - Mod( S + N ; 7 ) //number of days after last day of february ]; Date( 3 ; P ; Y ) ) Click to copy

Yet another formula to calculate easter.

The advantage of this one is that it follows the method by C.F.Gauss, published in 1800, that it's very short and does not depend on other custom functions.

It gives accurate dates from 1583 until 4000, beyond 4000 it's incorrect (filemaker doesn't calculate dates beyond 4000 anyway) and before 1583 the julian calandar was used and for that period this formula doesn't work either. For modernday use with the gregorian calander this formula suffices.

 

Comments

		Vaughan, Sydney AUstralia Oct 22, 2012
Great work. I have taken the liberty of using your code in a custom function I have created to work out holidays in Australia. I have given you credit in this new cf. HolidaysAUS() http://www.briandunning.com/cf/1494

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