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From: Thomas 'PointedEars' Lahn <PointedEars@web.de>
Newsgroups: comp.lang.javascript
Subject: Re: Measuring time (was: Random numbers)
Date: Sun, 29 Oct 2017 17:56:25 +0100
Organization: PointedEars Software (PES)
Lines: 66
Message-ID: <5089967.DvuYhMxLoT@PointedEars.de>
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Reply-To: Thomas 'PointedEars' Lahn <cljs@PointedEars.de>
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Dr J R Stockton wrote:

> […] Thomas 'PointedEars' Lahn wrote:
>> > On Tue, 24 Oct 2017 13:05:49 -0700 (PDT), Dr J R Stockton wrote:
>> >> IIRC, new Date(Y, 0, N) fails for years 0 to 99; and MD is wrong for
>> >> most of Year 0.
>> 
>> AFAICS, the result for Y === 0 is only wrong (not as specified) if N <
>> 366 and one expects a date that is not in 1900 CE.
> 
>              There is only one such date;

No, I meant if one expected a date in 1 BCE instead of 1900 CE.

>              there was no 1900-02-29.

| -> new Date(0, 0, 1)
| <- Mon Jan 01 1900 00:00:00 GMT+0100 (CET)
| 
| -> new Date(0, 1, 29)
| <- Thu Mar 01 1900 00:00:00 GMT+0100 (CET)
 
> But the following code yields merely 59 :-
>       S = ""
>       for (N=1 ; N<400 ; N++) {
>         D1 = new Date(0e3, 0, N).getDate()
>         D2 = new Date(2e3, 0, N).getDate()

Undeclared variable, unwise identifiers.

>         S += "+" + +(D1==D2) }

An Array instance is a lot more efficient for this:

  var a = [];

  for (…)
  {
    a.push("…");
  }

  var s = a.join("+");

>       eval(S)

Please don’t.

  var count = 0;

  for (var n = 1; n < 400; ++n)
  {
    var d1 = (new Date(0e3, 0, n)).getDate();
    var d2 = (new Date(2e3, 0, n)).getDate();
    count += +(d1 == d2);
  }

  console.log(count);
 
> In a normal year, January+February is 59 days; the rest are wrong.

I do not see your point.
 
-- 
PointedEars
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