1 files changed, 111 insertions, 0 deletions
diff --git a/misc_cmds/calendar/ostern.c b/misc_cmds/calendar/ostern.c
new file mode 100644
index 0000000..0f9d17e
--- /dev/null
+++ b/misc_cmds/calendar/ostern.c
@@ -0,0 +1,111 @@
+/*
+ * Copyright (c) 1996 Wolfram Schneider <wosch@FreeBSD.org>. Berlin.
+ * 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 AND CONTRIBUTORS ``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 AUTHOR 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 <sys/cdefs.h>
+__FBSDID("$FreeBSD: src/usr.bin/calendar/ostern.c,v 1.12 2007/05/07 11:18:30 dwmalone Exp $");
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+#include "calendar.h"
+
+/* return year day for Easter */
+
+/*
+ * This code is based on the Calendar FAQ's code for how to calculate
+ * easter is. This is the Gregorian calendar version. They refer to
+ * the Algorithm of Oudin in the "Explanatory Supplement to the
+ * Astronomical Almanac".
+ */
+
+int
+easter(int year) /* 0 ... abcd, NOT since 1900 */
+{
+    int G,	/* Golden number - 1 */
+	C,	/* Century */
+	H,	/* 23 - epact % 30 */
+	I,	/* days from 21 March to Paschal full moon */
+	J,	/* weekday of full moon */
+	L;	/* days from 21 March to Sunday on of before full moon */
+
+    G = year % 19;
+    C = year / 100;
+    H = (C - C/4 - (8*C+13)/25 + 19*G + 15) % 30;
+    I = H - (H/28)*(1 - (H/28)*(29/(H + 1))*((21 - G)/11));
+    J = (year + year/4 + I + 2 - C + C/4) % 7;
+
+    L = I - J;
+
+    if (year % 400 == 0 || (year % 4 == 0 && year % 100 != 0))
+	return 31 + 29 + 21 + L + 7;
+    else
+	return 31 + 28 + 21 + L + 7;
+}
+
+/* return year day for  Easter or easter depending days 
+ * Match: Easter([+-][0-9]+)?
+ * e.g: Easter-2 is  Good Friday (2 days before Easter)
+ */
+
+int
+geteaster(char *s, int year)
+{
+	int offset = 0;
+
+#define EASTER "easter"
+#define EASTERNAMELEN (sizeof(EASTER) - 1)
+
+	if (strncasecmp(s, EASTER, EASTERNAMELEN) == 0)
+	    s += EASTERNAMELEN;
+	else if (   neaster.name != NULL
+		 && strncasecmp(s, neaster.name, neaster.len) == 0
+		)
+	    s += neaster.len;
+	else
+	    return(0);
+
+#if DEBUG
+	printf("%s %d %d\n", s, year, EASTERNAMELEN);
+#endif
+
+	/* Easter+1  or Easter-2
+	 *       ^            ^   */
+
+	switch(*s) {
+
+	case '-':
+	case '+':
+	    offset = atoi(s);
+	    break;
+
+	default:
+	    offset = 0;
+	}
+	    
+	return (easter(year) + offset);
+}