From csus.edu!news.ucdavis.edu!agate!howland.reston.ans.net!EU.net!Belgium.EU.net!news Thu Jul 13 11:11:11 1995 Path: csus.edu!news.ucdavis.edu!agate!howland.reston.ans.net!EU.net!Belgium.EU.net!news From: Bruno Peeters Newsgroups: comp.software-eng,comp.lang.cobol,comp.lang.c++ Subject: Re: Date Algorithms - replies Date: Thu, 13 Jul 95 16:37:06 PDT Organization: EUnet Belgium, Leuven, Belgium Lines: 78 Message-ID: <3u3aho$6kr@news.Belgium.EU.net> References: <3te0ob$3s1@news.Belgium.EU.net> NNTP-Posting-Host: bruno.eunet.be Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Newsreader: NEWTNews & Chameleon -- TCP/IP for MS Windows from NetManage Xref: csus.edu comp.software-eng:30677 comp.lang.cobol:4165 comp.lang.c++:129745 My original posting >We are looking for algorithms or formulas that would help us in >a project of date management. What we need is to be able to >generate a calendar for a given year, as well in the past as >in the future. The limits would be the biggest possible >(actually our current algorithm is limited to 01/01/2100, >but we are doing some simulations that go over 75 to 100 years, >which means in the year 2000 we could begin to have some problem >with the date calculation). This calendar would show us the >holidays and movable feasts for the chosen land. This mean we >need some international calculation method not only limited >to a country. > >We would appreciate any help to find information on this topic : >existing algorithms, sources of information, ... I would like to thank everyone who contributed to my request. I have listed below all pointers that provided me with usefull information. Edward M. Reingold's Calendar Papers/Code are very usefull for everyone who is looking for conversion between Gregorian, ISO, Julian, Islamic and Hebrew calendars. Further information, can be found on http://emr.cs.uiuc.edu/home/reingold/public_html/calendars.html http://emr.cs.uiuc.edu/~reingold/calendars.html Emacs Lisp source code ftp://emr.cs.uiuc.edu:/pub/emacs/calendar/ LINUX contains a small utility that performs calculations with dates (CAL). LINUX source is available on several sites. I found the source code in the directory /games/cal.tar.gz. The site http://gauss.technion.ac.il:80/calendar/gauss/ contains several C programs dealing with Hebrew calendars and Gauss formula for passover. On CompuServe, in the MSMFC forum, a file (FORMUL.ZIP) can be found containing several date algorithms (such as Zeller's day of week formula, number of days between dates, how to calculate the date of Easter.). Several other forums on CompuServe also contains date and time utilities in various programming environments. Also on Compuserve, several files containing source code for various languages performing date calculations (day of the week, gregorian to and from julian date, ...). Dr. Dobb's Journal March 1993 contains an article 'Julian and Gregorian Calendars' written Peter JG Meyer, including source code. The July 1993 issue of Dr. Dobb's Journal contains an algorithm for determing the date of Easter written by Karl Hoppe. Other perhaps interesting references I found, but of which I did not get a copy yet : * Communications of the ACM RG Tantzen Conversions between calendar date and Julian day number vol 6, number 8, Augustus 1963 * Computer Language, March 1988, pp.9-10 * Acta Mathematica, 9, 1894, Chr. Zeller Someone provided me with two C programs * JDATE : To convert from Julian day to Gregorian calendar date * JULNUM : To return the absolute Julian number of any day since January 1, 4713 B.C. based on the above mentioned article in the Communications of the ACM. Again, many thanks to all repliers. Best regards, Bruno Peeters Gemeentekrediet