Gaußsche Osterformel

// Function that calculates the date of easter sunday as days after februar

// E.g. 32 would be 1. of april (Returns value: min. 22, max. 56)

int GetEasterSundayDateAsDaysAfterFebruary( int YEAR )

{

  int  k = YEAR / 100;    // K(X) = X div 100

  int s = 2 - (3*k + 3) / 4;  // S(K) = 2 - (3K + 3) div 4

  int m = 15 + (3*k + 3) / 4 - (8*k + 13) / 25;  // M(K) = 15 + (3K + 3) div 4 - (K + 13) div 25

  int a = YEAR % 19;  // A(X) = X mod 19

  int d = ( 19*a + m ) % 30;  // D(A,M) = (19A + M) mod 30

  //int r = (int) d / 29 + (int) d / 28 - (int) d / 29 - (int) a / 11;  // R(D,A) = D div 29 + (D div 28 - D div 29) (A div 11)

  int r = ( d + a / 11 ) / 29;  // Shorter Roegel version: R(D,A) = (D + A div 11) div 29

  int og = 21 + d - r;  // OG(D,R) = 21 + D - R

  int sz = 7 - ( YEAR + YEAR / 4 + s ) % 7;  // SZ(X,S) = 7 - (X + X div 4 + S) mod 7

  int oe = 7 - ( og - sz ) % 7;  // OE(OG,SZ) = 7 - (OG - SZ) mod 7

  return og + oe;

}