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Re: Date Conversion ?

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In comp.lang.javascript message <bhjavfFre0kU1@mid.individual.net>, Fri,
20 Dec 2013 09:52:57, Mel Smith <med_cutout_syntel@aol.com> posted:

>Dr. J said:
>
>> Show us your code, and we can think about whether they are reliably
>> solved.
>
>Hi Dr Stockton:
>
>    Here's my latest iteration of my date checking function (which includes
>JJ's parsedate() function and Thomas' Math function usage to find lows and
>highs.

JJ is inept. That function accepts dates before and after the end of the
month named.  Date checking is in the newsgroup FAQ, and on my Web site.
Form numbers for Y M' D, use nD = new Date(Date.UTC(Y, M', D)), and
check whether nD.getUTCMonth() agrees with M'.  IIRC, that method fails
for the end of February in Year Zero.  That's written from memory but is
at least about right - it assumes the date field is assuredly of no more
than two digits.

The original article did not mention date checking; if it is machine-
generated or already checked, there should be no need to check it again.

Your code uses local date routines.  Those, in temperate countries, are
substantially slower than UTC routines, since the date offset from GMT
must be found and used.

The Date Object is not needed, and its creation wastes time.  You can
extract the Mmm dd yy fields, convert Mmm to a number mm as already
described, and form  (yy*100+mm)*100+dd  which is easily seen to be an
integer rising by at least 1 at each midnight.  But, if you do check
with a Date Object, use its value for comparisons.

I do not know whether it will be quicker to load those into an array and
then use Math.(min|max).apply, or to just watch for increased or
decreased values.  If speed matters to you, you should test that and
report the result to enlighten the rest of us.

Your code is not executable as posted, for at least two reasons.  Never
allow your posting agent to line-wrap code.

I'm still not clear as to whether you want to find the values or the
positions or both for the earliest and latest dates.


-- 
 (c) John Stockton, nr London, UK.   E-mail, see Home Page.    Turnpike v6.05.
 Website  <http://www.merlyn.demon.co.uk/> - w. FAQish topics, links, acronyms
 PAS EXE etc. : <http://www.merlyn.demon.co.uk/programs/> - see in 00index.htm
 Dates - miscdate.htm estrdate.htm js-dates.htm pas-time.htm critdate.htm etc.

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Date Conversion ? "Mel Smith" <med_cutout_syntel@aol.com> - 2013-12-16 15:55 -0700
  Re: Date Conversion ? Bjoern Hoehrmann <bjoern@hoehrmann.de> - 2013-12-17 01:06 +0100
    Re: Date Conversion ? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-12-19 12:34 +0100
      Re: Date Conversion ? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-12-20 22:29 +0100
        Re: Date Conversion ? Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2013-12-23 10:00 -0200
  Re: Date Conversion ? JJ <duh@nah.meh> - 2013-12-17 07:06 +0700
    Re: Date Conversion ? Denis McMahon <denismfmcmahon@gmail.com> - 2013-12-17 00:35 +0000
      Re: Date Conversion ? "Mel Smith" <med_cutout_syntel@aol.com> - 2013-12-16 18:16 -0700
      Re: Date Conversion ? "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2013-12-17 10:09 +0100
        Re: Date Conversion ? Denis McMahon <denismfmcmahon@gmail.com> - 2013-12-17 17:02 +0000
        Re: Date Conversion ? Dr J R Stockton <reply1300@merlyn.demon.co.uk.invalid> - 2013-12-18 19:14 +0000
          Re: Date Conversion ? "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2013-12-19 15:42 +0100
            Re: Date Conversion ? "Michael F. Stemper" <michael.stemper@gmail.com> - 2013-12-19 09:20 -0600
              Re: Date Conversion ? "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2013-12-20 10:04 +0100
      Re: Date Conversion ? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-12-17 15:12 +0100
        Re: Date Conversion ? Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2013-12-17 18:10 -0200
          Re: Date Conversion ? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-12-17 21:42 +0100
    Re: Date Conversion ? Bjoern Hoehrmann <bjoern@hoehrmann.de> - 2013-12-18 13:36 +0100
  Re: Date Conversion ? Dr J R Stockton <reply1300@merlyn.demon.co.uk.invalid> - 2013-12-17 19:02 +0000
    Re: Date Conversion ? "Mel Smith" <med_cutout_syntel@aol.com> - 2013-12-17 20:51 -0700
      Re: Date Conversion ? Dr J R Stockton <reply1300@merlyn.demon.co.uk.invalid> - 2013-12-19 20:21 +0000
        Re: Date Conversion ? "Mel Smith" <med_cutout_syntel@aol.com> - 2013-12-20 09:52 -0700
          Re: Date Conversion ? Dr J R Stockton <reply1300@merlyn.demon.co.uk.invalid> - 2013-12-21 20:41 +0000
            Re: Date Conversion ? "Mel Smith" <med_cutout_syntel@aol.com> - 2013-12-22 09:52 -0700

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