A presentation at WordCamp Retreat Soltau 2018 in in 29614 Soltau, Germany by Andrey Savchenko
WP breaks time & how to fix it
2 Andrey “Rarst” Savchenko — Rarst.net — WP contractor — 1 Gs old — 310 Ms WP
3 Had you ever... changed WP time zone? Settings → General → Timezone
4 Had you ever... output localized time? date_i18n() , the_date() , etc.
5 A very brief history of time 1. solar time 2. city time 3. rail time 4. time zones 5. Universal Coordinated Time
6 Unix time 1 525 435 200 seconds since 1970–01–01 00:00:00 UTC
7 Unix time — consistent — storage–friendly — comparison–friendly — not human readable
8 PHP DateTime $dt = new DateTime(); echo $dt->getTimestamp(); 1525435200 echo $dt->format( DATE_RFC3339 ); 2018-05-04T14:00:00+02:00 echo $dt->getTimezone()->getName(); Europe/Berlin php.net/datetime
9 PHP DateTime — UTC–based — formatting — parsing — primarily English php.net/datetime
10 phpdatebook.com
12 WP time — PHP 4 code — partial PHP 5 retrofit — custom time zone logic — custom internationalization
13 WpDateTime — extends PHP DateTime classes — works around WP bugs — parses WP data github.com/Rarst/wpdatetime
14 WP time zone options setting gmt_offset timezone_string Berlin 2 'Europe/Berlin' UTC+2 '2' ''
15 WP time zone in all cases 1. get timezone_string 2. if empty — get gmt_offset 3. convert the offset number to ±00:00 (PHP 5.5+)
16 WpDateTimeZone to parse time zone $timezone = WpDateTimeZone::getWpTimezone(); setting $timezone->getName() Berlin 'Europe/Berlin' UTC+2 '+02:00'
17 date_i18n() DateTime date() date_i18n() language English English WP locale time zone arbitrary current PHP timezone_string input arbitrary timestamp “WP timestamp” formats date() date() date(), incomplete developer.wordpress.org/reference/functions/date_i18n
18 date_i18n() logic echo date_i18n( 'j. F Y, G.i \U\h\r T' );
19 date_i18n() fails w/ gmt_offset WP set to Berlin time zone: echo date_i18n( DATE_RFC3339 ); 2018-05-04T14:00:00+02:00 WP set to UTC+2 time zone: echo date_i18n( DATE_RFC3339 ); 2018-05-04T14:00:00+00:00 #34835
20 date_i18n() fails w/ Unix timestamp echo date( DATE_RFC3339, time() ); 2018-05-04T12:00:00+00:00 echo date_i18n( DATE_RFC3339, time() ); 2018-05-04T12:00:00+02:00 #38771
21 date_i18n() fails w/ some formats echo date_i18n( DATE_RFC3339 ); // === 'Y-m-d\TH:i:sP' 2018-05-04T14:00:00+02:00 echo date_i18n( 'c' ); // === 'c' 2018-05-04T14:00:00+00:00 echo date_i18n( DATE_RFC2822 ); // === 'D, d M Y H:i:s O' Fr, 04 Mai 2018 14:00:00 +0200 echo date_i18n( 'r' ); // === 'r' Fri, 04 May 2018 14:00:00 +0000 #20973
22 WpDateTime to wrap date_i18n() WP set to UTC+2 time zone: $time = new WpDateTime( '@' . time() ); $timezone = WpDateTimeZone::getWpTimezone(); $time = $time->setTimezone( $timezone ); echo $time->formatI18n( 'c' ); 2018-05-04T14:00:00+02:00 echo $time->formatI18n( 'r' ); Fr, 04 Mai 2018 14:00:00 +0200
23 post_date post_date post_date_gmt post_title 2018-05-04 13:00:00 2018-05-04 12:00:00 A post made in London WP set to London time zone: the_date( DATE_RFC3339 ); 2018-05-04T13:00:00+01:00
24 post_date fails w/ changed time zone post_date post_date_gmt post_title 2018-05-04 13:00:00 2018-05-04 12:00:00 A post made in London WP set to Berlin time zone: the_date( DATE_RFC3339 ); 2018-05-04T13:00:00+02:00 #38774
25 post_date in all cases 1. get post_date_gmt 2. if empty — get post_date 3. get WP time zone 4. adjust post_date[_gmt] with the time zone 5. convert to desired format
26 WpDateTime to parse post date post_date post_date_gmt post_title 2018-05-04 13:00:00 2018-05-04 12:00:00 A post made in London WP set to Berlin time zone: $time = WpDateTime::createFromPost( get_post() ); echo $time->formatI18n( DATE_RFC3339 ); 2018-05-04T14:00:00+02:00
27 Takeaways — WP gets time storage and output wrong — read and use UTC time — write timestamp, UTC, or RFC 3339 — use DateTime to operate time — use WpDateTime to bridge WP and PHP
28 Thank you for your time! Questions? twitter.com/Rarst Rarst.net/slides/time
29 Image credits — Photo by Adina Voicu CC0 — Photo by Eugene Shelestov CC0
Date/Time component of WordPress core dates back to ancient PHP 4 times.
As result work with dates, times, and timezones is full of pitfalls. Trivial actions in admin and code can lead to massive errors in output of time information. Errors that will confuse both people and software.
The talk will summarize years of experience with bugs and edge cases in Date/Time component. Point out the most common (and trivial to make!) errors. Provide practical solutions for robust development and output practices.
The following resources were mentioned during the presentation or are useful additional information.
Original slides for the presentation.
If your development involves working with dates and times, then this book is a must-have. In this book, Derick Rethans (contributor to PHP’s core date extension and well-known PHP expert) explores in great detail the subtle nuances of working with dates and times.
Extension of PHP’s DateTime and DateTimeZone classes for WordPress context.
Here’s what was said about this presentation on social media.
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