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# Question Concerning Date Function Range

 P: n/a After reading section 15.9.1.1 the ECMAScript Language Specifications I see that the date range for the Date function is +/- 100,000,000 days from 01 Jan 1970. This is called an extrapolated Gregorian calendar. Since the Gregorian calendar did not begin until 15 Oct 1582 what is the purpose of dates before that date? Wouldn't any computation prior to that date be meaningless or am I missing something? The reason I ask is that I have created a date calculator at my web site. I don't want it to do computations with dates that have no meaning. Columbus discovered america on 12 Oct 1492. This must have been with the Julian Calendar. If I used the Date function to see how many days it was from that date until now would it be correct? -- Dennis M. Marks http://www.dcs-chico.com/~denmarks/ Replace domain.invalid with dcsi.net -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- Jul 23 '05 #1
5 Replies

 P: n/a JRS: In article <14*************************@domain.invalid>, seen in news:comp.lang.javascript, Dennis M. Marks posted at Wed, 14 Apr 2004 17:42:43 : After reading section 15.9.1.1 the ECMAScript Language Specifications Isee that the date range for the Date function is +/- 100,000,000 daysfrom 01 Jan 1970. And if you read it more carefully, you will find that it is from 1970-01-01 00:00:00 *UTC*. It is important to remember that the millisecond count is Greenwich-based. Since the Gregorian calendar did not begin until 15 Oct 1582 what isthe purpose of dates before that date? Wouldn't any computation priorto that date be meaningless or am I missing something? Yes; to the latter. The proleptic Gregorian calendar refers in present terms to dates before the relevant Julian-Gregorian transition; the Julian calendar refers to the terms used at the time - though one should be aware of the difference between O.S. and N.S. dating. It is easier to calculate with a single, consistent, non-saltatory calendar. The Julian Calendar is needed only for work dealing with ancient records. Scaliger chose BC 4713-01-01 noon to start his day-count : on the proleptic Julian Calendar, of course, as Caesar was at that time minus four-and-a-half millennia old. Archbishop Ussher of Armagh likewise calculated the date of the Creation in Julian, likewise proleptic. All B.C. dates, indeed all dates up to about A.D. 525 and most dates for a while thereafter, are proleptic. Indeed, it's hard to think of a date or day scale whose origin is not proleptic. The reason I ask is that I have created a date calculator at my website. I don't want it to do computations with dates that have nomeaning.Columbus discovered america on 12 Oct 1492. He did not. He reached an outlying part of the American continents; it was Friday 1492-10-21 proleptic Gregorian. BTW, Zeller correctly describes the event as the discovery of the new world, or as a landing; he does not use the word Amerika (and would not have had a word to use in the 1883 paper). This must have been withthe Julian Calendar. If I used the Date function to see how many daysit was from that date until now would it be correct? One cannot predict what results you might produce; but as-distributed javascript takes all dates as Gregorian. It was, currently, 186815 days ago, making due allowance for the calendar change; MJD -133705 (today is +53110). -- © John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v4.00 MIME. © TP/BP/Delphi/&c., FAQqy topics & links; RAH Prins : c.l.p.b mFAQ; Timo Salmi's Turbo Pascal FAQ. Jul 23 '05 #2

 P: n/a In article , Dr John Stockton wrote: Columbus discovered america on 12 Oct 1492. He did not. He reached an outlying part of the American continents; it was Friday 1492-10-21 proleptic Gregorian. BTW, Zeller correctly describes the event as the discovery of the new world, or as a landing; he does not use the word Amerika (and would not have had a word to use in the 1883 paper). This must have been withthe Julian Calendar. If I used the Date function to see how many daysit was from that date until now would it be correct? One cannot predict what results you might produce; but as-distributed javascript takes all dates as Gregorian. It was, currently, 186815 days ago, making due allowance for the calendar change; MJD -133705 (today is +53110). Thank you for your help. Since Columbus Day is celebrated on 12 Oct (1492) in the U.S. I just wondered what calendar this date is based on. Do I assume extrapolated Gregorian? Is there a year zero in the Gregorian calendar? -- Dennis M. Marks http://www.dcs-chico.com/~denmarks/ Replace domain.invalid with dcsi.net -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- Jul 23 '05 #3

 P: n/a In article <15*************************@domain.invalid>, Dennis M. Marks wrote: In article , Dr John Stockton wrote: Columbus discovered america on 12 Oct 1492. He did not. He reached an outlying part of the American continents; it was Friday 1492-10-21 proleptic Gregorian. BTW, Zeller correctly describes the event as the discovery of the new world, or as a landing; he does not use the word Amerika (and would not have had a word to use in the 1883 paper). This must have been withthe Julian Calendar. If I used the Date function to see how many daysit was from that date until now would it be correct? One cannot predict what results you might produce; but as-distributed javascript takes all dates as Gregorian. It was, currently, 186815 days ago, making due allowance for the calendar change; MJD -133705 (today is +53110). Thank you for your help. Since Columbus Day is celebrated on 12 Oct (1492) in the U.S. I just wondered what calendar this date is based on. Do I assume extrapolated Gregorian? Is there a year zero in the Gregorian calendar? More questions (It never ends, does it?) I have found out that negative years return a B.C. date that is one year less. -1 returns 2 B.C. 0-99 returns 1900-1999. How do I enter the actual years 0-99 (where 0 is actually 1 B.C. and 1 is 1 CE or AD)? -- Dennis M. Marks http://www.dcs-chico.com/~denmarks/ Replace domain.invalid with dcsi.net -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- Jul 23 '05 #4

 P: n/a JRS: In article <15*************************@domain.invalid>, seen in news:comp.lang.javascript, Dennis M. Marks posted at Thu, 15 Apr 2004 17:29:17 :Since Columbus Day is celebrated on 12 Oct (1492) in the U.S. I justwondered what calendar this date is based on. Do I assume extrapolatedGregorian? The date 12 Oct 1492 is a Julian date. Historians almost always use a current date notation. Zeller, for example, uses it as a Julian example date in three of his papers (and, if he got it wrong the first time, one can expect that he would have been corrected in time for the last). The US thus celebrates, on a day which is not an anniversary, an event which was not the discovery of America. Is there a year zero in the Gregorian calendar? The customary notation has 2 BC, 1 BC, 1 AD, 2 AD - which is in proper accordance with the meanings of BC & AD. Astronomer's notation has -2, -1, 0, -1, -2. Both of those can be used with Julian and Gregorian. AISB, see below. -- © John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v4.00 MIME. © Web - w. FAQish topics, links, acronyms PAS EXE etc : - see 00index.htm Dates - miscdate.htm moredate.htm js-dates.htm pas-time.htm critdate.htm etc. Jul 23 '05 #5

 P: n/a JRS: In article <15*************************@domain.invalid>, seen in news:comp.lang.javascript, Dennis M. Marks posted at Thu, 15 Apr 2004 17:55:15 : More questions (It never ends, does it?)I have found out that negative years return a B.C. date that is oneyear less. -1 returns 2 B.C. That is well-known; a year denoted solely by a number smaller than 1 can only be in astronomical notation. 0-99 returns 1900-1999. That is because primitive Californian(?) programmers, back in the mists of time probably before some here were born, did not foresee that there might be time after the year '99 (even though it had already happened once in that State). It would have been far better to implement a primitive new Date which treated all years straightforwardly, and a new Method to window a date into a desired 100-year range, absolute or relative to the current year. How do I enter the actual years 0-99 (where 0 is actually 1 B.C. and 1is 1 CE or AD)? If you were to read the FAQ on the subject of dates, you would know how to find that out; see sig. below. One way is to add 100 to the year and subtract 1200 from the month. A better is to use D = new Date(0) // if needed D.setHours(0,0,0,0) D.setFullYear(Y, M-1, D) However, thought may be needed about what happens, in Spring and in Autumn, if the seasonal clock change involves Y-M-D 00:00:00, local time. Anyone from the Azores or East Greenland reading this? -- © John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v4.00 IE 4 © Jim Ley's FAQ for news:comp.lang.javascript jscr maths, dates, sources. TP/BP/Delphi/jscr/&c, FAQ items, links. Jul 23 '05 #6

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