Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uwm.edu!lll-winken!decwrl!ucbvax!SCFVM.BITNET!Z8WGH From: Z8WGH@SCFVM.BITNET (Bill Hecox) Newsgroups: comp.lang.asm370 Subject: Re: leap years, julian date, and stuff. Message-ID: <9001041929.AA10370@brazos.rice.edu> Date: 4 Jan 90 18:43:05 GMT References: Sender: daemon@ucbvax.BERKELEY.EDU Reply-To: IBM 370 Assembly Programming Discussion List Distribution: inet Organization: The Internet Lines: 35 >Since we're sort of on the subject, I have been looking for an algorithm >to calculate the day-of-week from the date. If anyone has this >algorithm, could you please send me the pseudo code directly? I do >not subscribe to this group. Thank you so much. -Bob Peraino I have always used this method. The last two digits of the year Plus the Julian day divided by 4 (round up) Plus the julian day (1 to 366) Divide all this by 7 Remainder of 0 = SAT 1 = SUN This method will work until Dec 31, 1999 The method works on the idea that the first day of this century was a specific day of the week. Jan 1, 1900 The current year is added because there is one more day in each year since 1900 then there is a multiple of seven. I.E. 7 X 52 = 364 + 1 = 365 The current year divided by 4 (rounded up) is used to account for the extra day in each leap year since 1900. The Julian day is added to account for the offset into the current year. I would be interested in seeing other methods. Also methods that will work past the end of the century. Regards; Bill Hecox