Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10 Apollo 10/31/84; site apollo.uucp Path: utzoo!watmath!clyde!bonnie!akgua!whuxlm!harpo!decvax!wivax!apollo!nazgul From: nazgul@apollo.uucp (Kee Hinckley) Newsgroups: net.sources Subject: RE: Algorithm wanted Message-ID: <236aa00f.8e4@apollo.uucp> Date: Fri, 7-Dec-84 14:37:39 EST Article-I.D.: apollo.236aa00f.8e4 Posted: Fri Dec 7 14:37:39 1984 Date-Received: Sun, 9-Dec-84 02:39:38 EST Organization: Apollo Computer, Chelmsford, Mass. Lines: 59 .... This is taken from a posting of parsedate a while back. If I had more time I would comment this excerpt with an explanation, but.... I'll leave it as an exercise to the reader. ............................................................................. DATE MANIPULATION PACKAGE Richard B. Wales UCLA Center for Experimental Computer Science Copyright (c) 1984 by Richard B. Wales The author hereby grants permission to use or redistribute this package freely and without charge, subject to the following restrictions: (1) The copyright notice must be retained in all copies of the source. (2) Any changes made to the source must be clearly documented (such as by #ifdef's or by use of a source-code control system such as RCS or SCCS), so that the original version of the source as distributed by the author can be reconstructed if necessary and distinguished from modifications made by others. struct parsedate { long unixtime; /* UNIX internal representation of time */ char *error; /* NULL = OK; non-NULL = error */ int year; /* year (1600 on) */ int month; /* month (1-12) */ int day; /* day of month (1-31) */ int hour; /* hour (0-23) */ int minute; /* minute (0-59) */ int second; /* second (0-59) */ int zone; /* time zone offset in minutes -- "+" or "-" */ int dst; /* daylight savings time (0 = no, 1 = yes) */ int weekday; /* real day of week (0-6; 0 = Sunday) */ int c_weekday; /* claimed day of week (0-6; 0 = Sunday) */ }; struct parsedate *pd; /* Compute the day of the week. The next several lines constitute a * perpetual-calendar formula. Note, of course, that the "claimed" * day of the week (pd->c_weekday) is ignored here. */ if (pd->year > 0 && pd->month > 0 && pd->day > 0) { if (pd->month >= 3) n = pd->year / 100, l = pd->year % 100; else n = (pd->year-1) / 100, l = (pd->year-1) % 100; a = (26 * ((pd->month+9)%12 + 1) - 2) / 10; weekday = (a+(l>>2)+(n>>2)+l-(n+n)+pd->day); while (weekday < 0) weekday += 7; pd->weekday = weekday % 7; } ......................................................................... Kee Hinckley ...decvax!wivax!apollo!nazgul