From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 11390f,be6b7e036aa9236c X-Google-Attributes: gid11390f,public X-Google-Thread: 1094ba,be6b7e036aa9236c X-Google-Attributes: gid1094ba,public X-Google-Thread: 103376,be6b7e036aa9236c X-Google-Attributes: gid103376,public X-Google-Thread: 1014db,be6b7e036aa9236c X-Google-Attributes: gid1014db,public X-Google-Thread: fa0ae,be6b7e036aa9236c X-Google-Attributes: gidfa0ae,public X-Google-Thread: 10261c,68666e29d0425009 X-Google-Attributes: gid10261c,public X-Google-Thread: 114809,68666e29d0425009 X-Google-Attributes: gid114809,public X-Google-Thread: 1164ba,be6b7e036aa9236c X-Google-Attributes: gid1164ba,public From: Dr John Stockton Subject: Re: Results of my test: Re: Friday 13th, try it yourself Date: 1996/09/26 Message-ID: <5bxuvOAdKcSyEwne@merlyn.demon.co.uk>#1/1 X-Deja-AN: 185420321 distribution: world x-nntp-posting-host: merlyn.demon.co.uk references: <52bmft$f3l@news1.halcyon.com> organization: Home, Surrey, UK mime-version: 1.0 newsgroups: comp.lang.ada,comp.lang.apl,comp.lang.basic,comp.lang.c,comp.lang.fortran,comp.lang.perl.misc,comp.lang.pascal.misc,comp.lang.smalltalk Date: 1996-09-26T00:00:00+00:00 List-Id: In article of Wed, 25 Sep 1996 16:25:19 in comp.lang.pascal.misc, Lee Crites wrote: > >For the most part, I've ignored this friday the 13th thread. However, >something someone said got my interest. Basically the statement was that >the same date 400 years later would fall on the same day. I thought I'd >check it out and see. Unfortunately, it did not work on the dates I >checked. SNIP Too complex. Just consider 400 years 400 * 365 Taking all years as ordinary + 100 but every fourth is leap - 4 apart from the centuries + 1 except for every fourth. ========= 146097 ; * 1/7 => 20871.0 = integer weeks in 400 years. The calendar therefore repeats every 400 years. This calculation can be done in one's head, without even a calculator. In 400 years there are 4800 months each containing one 13th. Some are Sunday, some ... ...Saturday; but 4800/7 is not an integer, so the 13ths cannot be evenly distributed among the days of the week. I think it is now necessary to do a little real work; there are 14 types of year (Leap or not, starting Sun .. Sat), and the number of each type in 400 years can be counted; and each type contributes a certain number of 13ths. It might be easier to consider the year as starting on March 1st; there are now only 7 types of year for 13th-counting. -- John Stockton, Surrey, UK. JRS@merlyn.demon.co.uk Turnpike v1.12 MIME http://www.merlyn.demon.co.uk/