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Groups > comp.lang.javascript > #26133
| From | Thomas 'PointedEars' Lahn <PointedEars@web.de> |
|---|---|
| Newsgroups | comp.lang.javascript |
| Subject | Re: Date arithmetic |
| Date | 2014-11-13 21:26 +0100 |
| Organization | PointedEars Software (PES) |
| Message-ID | <6814026.8sujcrue1K@PointedEars.de> (permalink) |
| References | (2 earlier) <m3u1bl$8ha$1@speranza.aioe.org> <111120142237479787%timstreater@greenbee.net> <m3udpq$m9v$1@solani.org> <XnsA3E354F8EA950eejj99@194.109.133.133> <m42f3g$d4d$1@solani.org> |
Christoph M. Becker wrote:
> In the given case (there is no time involved), I would work around any
> potential DST issues by using Date.UTC(). Parsing the date strings is
> slightly more complex, but the calculations should be exact (not even
> Math.round() is needed).
>
> function daysBetween(isoDay1, isoDay2) {
> var msPerDay = 24 * 60 * 60 * 1000,
You can skip that inefficient computation on each call (unless optimized) by
using the easy-to-remember value 864e5 (there are 86'400 seconds in a
standard day).
> isoExp = /^\s*(\d{4})-(\d\d)-(\d\d)\s*$/,
> parts, timestamp1, timestamp2;
>
> parts = isoExp.exec(isoDay1);
I find
parts = isoDay1.match(isoExp);
easier to read. I use RegExp.prototype.exec() only in loops, such as with
parsers, because with global matching there is no other way to get at the
submatches.
That said, such a function should be passed two references to Date instances
or two UTC timestamps, and leave the parsing to the caller.
> timestamp1 = Date.UTC(parts[1], parts[2] - 1, parts[3]);
> parts = isoExp.exec(isoDay2);
> timestamp2 = Date.UTC(parts[1], parts[2] - 1, parts[3]);
>
> return Math.abs(timestamp2 - timestamp1) / msPerDay;
> }
Good idea.
However, you may want to skip the Math.abs() to give an indication to the
caller which date is in the future of the other. Rounding should also be
considered because those values are internally represented as floating-point
values.
JFTR, JSX:date.js (see sig) contains jsx.date.dayOfYear() and optionally
provides Date.prototype.getDayOfYear() which can also be used to compute the
difference. But your approach is more elegant and does not require
consideration of years in-between and leap years. I do not think it can
fail.
For this use-case you should consider adding 1 unless the “days” to pay for
are actually nights (from January 1 to January 5, for example, there are *5*
days, but 4 *nights*). Insofar daysBetween() is misleading, too. Maybe
other APIs can provide for a better name.
--
PointedEars
FAQ: <http://PointedEars.de/faq> | SVN: <http://PointedEars.de/wsvn/>
Twitter: @PointedEars2 | ES Matrix: <http://PointedEars.de/es-matrix>
Please do not Cc: me. / Bitte keine Kopien per E-Mail.
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Date arithmetic Swifty <steve.j.swift@gmail.com> - 2014-11-11 12:38 +0000
Re: Date arithmetic "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2014-11-11 15:10 +0100
Re: Date arithmetic Swifty <steve.j.swift@gmail.com> - 2014-11-11 22:07 +0000
Re: Date arithmetic Tim Streater <timstreater@greenbee.net> - 2014-11-11 22:37 +0000
Re: Date arithmetic "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-12 02:40 +0100
Re: Date arithmetic "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2014-11-12 08:21 +0100
Re: Date arithmetic "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-13 15:27 +0100
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-13 21:26 +0100
Re: Date arithmetic "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-14 14:16 +0100
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-15 07:13 +0100
Re: Date arithmetic Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-11-15 19:36 +0000
Re: Date arithmetic "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-16 17:24 +0100
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-16 18:49 +0100
Re: Date arithmetic "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-17 00:14 +0100
Re: Date arithmetic Dr J R Stockton <J.R.Stockton@physics.org> - 2014-11-16 10:51 -0800
Re: Date arithmetic "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2014-11-16 20:17 +0100
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-17 00:52 +0100
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-17 01:11 +0100
Re: Date arithmetic Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-11-18 16:18 +0000
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-19 11:00 +0100
Re: Date arithmetic Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-11-21 22:58 +0000
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-22 18:33 +0100
Re: Date arithmetic Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-11-23 19:38 +0000
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-24 01:14 +0100
Re: Date arithmetic Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-11-25 21:17 +0000
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-26 18:25 +0100
Re: Date arithmetic Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-11-27 19:34 +0000
Re: Date arithmetic "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-28 01:25 +0100
Re: Date arithmetic Dr J R Stockton <J.R.Stockton@physics.org> - 2014-11-28 05:29 -0800
Re: Date arithmetic Andrew Poulos <ap_prog@hotmail.com> - 2014-11-28 11:44 +1100
Re: Date arithmetic Dr J R Stockton <J.R.Stockton@physics.org> - 2014-11-28 04:52 -0800
Re: Date arithmetic "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-28 14:24 +0100
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-28 14:47 +0100
Re: Date arithmetic Dr J R Stockton <J.R.Stockton@physics.org> - 2014-11-28 06:12 -0800
Re: Date arithmetic Andrew Poulos <ap_prog@hotmail.com> - 2014-11-29 16:59 +1100
Re: Date arithmetic John Harris <niam@jghnorth.org.uk.invalid> - 2014-11-29 20:05 +0000
Re: Date arithmetic Joao Rodrigues <groups_jr-1@yahoo.com> - 2014-11-29 23:47 -0200
Re: Date arithmetic Andrew Poulos <ap_prog@hotmail.com> - 2014-12-01 10:44 +1100
Re: Date arithmetic Tim Streater <timstreater@greenbee.net> - 2014-11-30 23:54 +0000
Re: Date arithmetic Andrew Poulos <ap_prog@hotmail.com> - 2014-12-01 13:01 +1100
Re: Date arithmetic "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-17 01:34 +0100
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-17 01:41 +0100
Re: Date arithmetic "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-18 19:06 +0100
Re: Date arithmetic Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-11-18 16:26 +0000
Re: Date arithmetic "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-19 17:52 +0100
Re: Date arithmetic Gene Wirchenko <genew@telus.net> - 2014-11-19 09:44 -0800
Re: Date arithmetic "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2014-11-19 19:34 +0100
Re: Date arithmetic Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-11-19 19:13 +0000
Re: Date arithmetic "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2014-11-19 22:18 +0100
Re: Date arithmetic Gene Wirchenko <genew@telus.net> - 2014-11-19 13:43 -0800
Re: Date arithmetic Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-11-19 22:40 +0000
Re: Date arithmetic Tim Streater <timstreater@greenbee.net> - 2014-11-19 22:51 +0000
Re: Date arithmetic Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-11-19 23:35 +0000
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-19 23:10 +0100
Re: Date arithmetic Tim Streater <timstreater@greenbee.net> - 2014-11-19 22:32 +0000
Re: Date arithmetic Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-11-19 23:26 +0000
Re: Date arithmetic "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-20 00:47 +0100
Re: Date arithmetic Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-11-20 00:17 +0000
Re: Date arithmetic Dr J R Stockton <J.R.Stockton@physics.org> - 2014-11-20 01:18 -0800
Re: Date arithmetic Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-11-20 13:47 +0000
Re: Date arithmetic Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-11-21 22:29 +0000
Re: Date arithmetic Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2014-11-19 19:24 -0200
Re: Date arithmetic Gene Wirchenko <genew@telus.net> - 2014-11-19 13:40 -0800
Re: Date arithmetic "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-19 23:40 +0100
Re: Date arithmetic Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-11-18 16:44 +0000
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-19 11:20 +0100
Re: Date arithmetic Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-11-14 20:45 +0000
Re: Date arithmetic "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2014-11-15 14:13 -0800
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-15 23:42 +0100
Re: Date arithmetic "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2014-11-12 00:23 +0100
Re: Date arithmetic Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-11-12 13:24 +0000
Re: Date arithmetic "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-12 14:43 +0100
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-12 19:48 +0100
Re: Date arithmetic "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-13 01:18 +0100
Re: Date arithmetic Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-11-12 20:19 +0000
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-13 03:42 +0100
Re: Date arithmetic Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-11-12 20:06 +0000
Re: Date arithmetic RobG <rgqld@iinet.net.au> - 2014-11-23 20:51 -0800
Re: Date arithmetic Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-11-25 20:08 +0000
Re: Date arithmetic "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-26 01:31 +0100
Re: Date arithmetic RobG <rgqld@iinet.net.au> - 2014-12-08 19:42 -0800
Re: Date arithmetic "Christoph M. Becker" <cmbecker69@arcor.de> - 2014-11-26 01:40 +0100
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-26 22:07 +0100
Re: Date arithmetic RobG <rgqld@iinet.net.au> - 2014-12-08 21:41 -0800
Re: Date arithmetic "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2014-12-09 09:47 +0100
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-12-09 14:17 +0100
Re: Date arithmetic Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-12-10 23:34 +0000
Re: Date arithmetic RobG <rgqld@iinet.net.au> - 2014-12-10 17:21 -0800
Re: Date arithmetic Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-12-13 17:19 +0000
Re: Date arithmetic RobG <rgqld@iinet.net.au> - 2014-12-10 18:35 -0800
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-11 22:29 +0100
Re: Date arithmetic Swifty <steve.j.swift@gmail.com> - 2014-11-11 21:53 +0000
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-11 23:43 +0100
Re: Date arithmetic John Harris <niam@jghnorth.org.uk.invalid> - 2014-11-12 15:49 +0000
Re: Date arithmetic Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-11-12 19:58 +0000
Re: Date arithmetic Dr.Kral@nyc.rr.com - 2014-11-13 20:24 -0500
Re: Date arithmetic Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-11-14 04:34 +0100
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