paskha.c revision 218797
1/*- 2 * Copyright (C) 1993-1996 by Andrey A. Chernov, Moscow, Russia. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 */ 26 27#include <sys/cdefs.h> 28__FBSDID("$FreeBSD: head/usr.bin/calendar/paskha.c 218797 2011-02-18 13:41:45Z osa $"); 29 30#include <stdio.h> 31#include <stdlib.h> 32#include <string.h> 33 34#include "calendar.h" 35 36#define PASKHA "paskha" 37#define PASKHALEN (sizeof(PASKHA) - 1) 38 39/* return difference in days between Julian and Gregorian calendars */ 40int 41j2g(int year) 42{ 43 return (year < 1500) ? 44 0 : 45 10 + (year/100 - 16) - ((year/100 - 16) / 4); 46} 47 48/* return year day for Orthodox Easter using Gauss formula */ 49/* (new style result) */ 50 51int 52paskha(int R) /*year*/ 53{ 54 int a, b, c, d, e; 55 static int x = 15; 56 static int y = 6; 57 int *cumday; 58 59 a = R % 19; 60 b = R % 4; 61 c = R % 7; 62 d = (19 * a + x) % 30; 63 e = (2 * b + 4 * c + 6 * d + y) % 7; 64 cumday = cumdaytab[isleap(R)]; 65 return (((cumday[3] + 1) + 22) + (d + e) + j2g(R)); 66} 67