1 files changed, 54 insertions, 0 deletions
diff --git a/src/usr.bin/calendar/paskha.c b/src/usr.bin/calendar/paskha.c
new file mode 100644
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--- /dev/null
+++ b/src/usr.bin/calendar/paskha.c
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+/*	$OpenBSD: paskha.c,v 1.6 2009/10/27 23:59:36 deraadt Exp $	*/
+
+/*
+ * Copyright (C) 1993-1996 by Andrey A. Chernov, Moscow, Russia.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <stdio.h>
+#include <tzfile.h>
+
+#include "calendar.h"
+
+/* return year day for Orthodox Easter using Gauss formula */
+/* (new style result); subtract 13 for old style */
+
+int
+paskha(int R)  /*year*/
+{
+	int a, b, c, d, e;
+	static int x = 15;
+	static int y = 6;
+	int cumdays;
+
+	a = R % 19;
+	b = R % 4;
+	c = R % 7;
+	d = (19*a + x) % 30;
+	e = (2*b + 4*c + 6*d + y) % 7;
+	cumdays = 31 + 28;
+	if (isleap(R))
+		cumdays++;
+	return ((cumdays + 22) + (d + e) + 13);
+}