Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/5/84; site ur-cvsvax.UUCP Path: utzoo!watmath!clyde!bonnie!akgua!whuxlm!harpo!decvax!linus!philabs!cmcl2!seismo!rochester!ur-cvsvax!bill From: bill@ur-cvsvax.UUCP (Bill Vaughn) Newsgroups: net.bugs,net.puzzle Subject: Re: Re: Computer bugs in the year 3200 Message-ID: <169@ur-cvsvax.UUCP> Date: Fri, 15-Feb-85 10:44:40 EST Article-I.D.: ur-cvsva.169 Posted: Fri Feb 15 10:44:40 1985 Date-Received: Mon, 18-Feb-85 05:49:17 EST References: <246@cheviot.UUCP> <974@utastro.UUCP> <7927@brl-tgr.ARPA> <587@vu44.UUCP> Distribution: net Organization: Center for Visual Science, U. of Rochester Lines: 41 Xref: watmath net.bugs:552 net.puzzle:557 > In article <7927@brl-tgr.ARPA> ron@brl-tgr.ARPA (Ron Natalie ) writes: > >> For those of you fixing things in your software: > >> > >> The year 2000 *is* a leap year, despite what many algorithms tell you. > >> The year 2400 is *not* a leap year. > >> > >> With minimal effort, you can make things work until 2399. You may be > >> subject to complaints after that. > >> > >Now you've really got me confused. Why is 2400 not a leap year? > > (msd = mean solar day) > 1 year = 365.2422 msd = 365 + 1/4 - 1/100 + 1/400 + error > That's why we have: > leapyear 1 out of 4 > non leap year 1 out of 100 > leapyear 1 out of 400 (So 2400 is a leap year.) > Read any basic astronomy book. > -- Hmmm. Let's take this two more steps. Since our error over the long run will be +0.0003 msd, we can reduce this by taking a leap year back every 3200 years making the error now -0.0000125 msd. But this can be corrected by replacing one of those leap years we just took back every 80,000 years and we're right on the money, assuming 365.2422 msd/year is exact and that it's constant over this period of time. I'm sure neither of these assumptions are correct ;-). So, for the time being, I claim that 3200 should *not* be a leap year, (nor should any year divisible by 3200, except if it's also divisible by 80,000). OK you hackers, I want those algorithms updated tomorrow. :-) Bill Vaughn UNIV. OF ROCHESTER Center for Visual Science {allegra,seismo,decvax}!rochester!ur-cvsvax!bill Guru: What's the matter? Novice hacker: When I do this, it hurts. (shows guru his core dump) Guru: DON'T DO THAT!!