A presentation at WordCamp Bucharest 2018 in in Bucharest, Romania by Andrey Savchenko
WP breaks time & how to fix it
2 Andrey “Rarst” Savchenko — Rarst.net — WP contractor — 1 Gs old — 325 Ms WP — Date/Time maintainer
3 Had you ever... changed WP time zone? Settings → General → Timezone
4 Had you ever... output localized time? date_i18n() , the_date() , etc.
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6 A very brief history of time 1. solar time 2. city time 3. rail time 4. time zones 5. Universal Coordinated Time
7 Unix time 1 540 645 200 seconds since 1970–01–01 00:00:00 UTC
8 Unix time — consistent — storage–friendly — comparison–friendly — not human readable
9 PHP DateTime $dt = new DateTime(); echo $dt->getTimestamp(); 1540645200 echo $dt->format( DATE_RFC3339 ); 2018-10-27T16:00:00+03:00 echo $dt->getTimezone()->getName(); Europe/Bucharest php.net/datetime
10 PHP DateTime — UTC–based — formatting — parsing — primarily English php.net/datetime
11 phpdatebook.com
13 WP time — PHP 4 code — partial PHP 5 retrofit — custom time zone logic — custom internationalization
14 WpDateTime — extends PHP DateTime classes — works around WP bugs — parses WP data github.com/Rarst/wpdatetime
15 wp_date (work in progress...) — core bugs audit & fixes — unified timezone processing — real timestamps & canonical UTC github.com/Rarst/wp-date
16 WP time zone options setting gmt_offset timezone_string Bucharest 3 'Europe/Bucharest' UTC+3 '3' '' #44985
17 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+)
18 WpDateTimeZone to parse time zone $timezone = WpDateTimeZone::getWpTimezone(); setting $timezone->getName() Bucharest 'Europe/Bucharest' UTC+3 '+03:00' Hopefully in wp_date: wp_timezone()
19 date_i18n() DateTime date() date_i18n() language English English WP locale time zone arbitrary current PHP current WP input arbitrary timestamp “WP timestamp” formats date() date() date(), incomplete developer.wordpress.org/reference/functions/date_i18n Hopefully in wp_date: wp_date()
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21 date_i18n() logic echo date_i18n( 'j F Y, \o\r\a G:i T' ); 1. j F Y, \o\r\a G:i T 2. j \o\c\t\o\m\b\r\i\e Y, \o\r\a G:i T — locale 3. j \o\c\t\o\m\b\r\i\e Y, \o\r\a G:i \E\E\S\T — zone 4. 27 octombrie 2018, ora 16:00 EEST — date()
22 date_i18n() fails w/ Unix timestamp echo date( DATE_RFC3339, time() ); 2018-10-27T13:00:00+00:00 echo date_i18n( DATE_RFC3339, time() ); 2018-10-27T13:00:00+03:00 #38771
23 post_date post_date post_date_gmt post_title 2018-10-27 14:00:00 2018-10-27 13:00:00 A post made in London WP set to London time zone: the_date( DATE_RFC3339 ); 2018-10-27T14:00:00+01:00
24 post_date fails w/ changed time zone post_date post_date_gmt post_title 2018-10-27 14:00:00 2018-10-27 13:00:00 A post made in London WP set to Bucharest time zone: the_date( DATE_RFC3339 ); 2018-10-27T14:00:00+03:00 #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 2018-10-27 14:00:00 2018-10-27 13:00:00 A post made in London WP set to Bucharest time zone: $time = WpDateTime::createFromPost( get_post() ); echo $time->formatI18n( DATE_RFC3339 ); 2018-10-27T16:00:00+03:00 Hopefully in wp_date: canonical UTC.
27 Takeaways — WP gets time storage and output wrong — read UTC time; write timestamp, UTC, or RFC 3339 — use DateTime to operate time — use WpDateTime to bridge WP and PHP — hope wp_date works out
28 Thank you for your time! Questions? twitter.com/Rarst wordpress.slack.com/messages/core-datetime Rarst.net/slides/time-buc
29 Image credits — Photo by Adina Voicu CC0 — “Time” comic by Zach Weinersmith — 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.
The initiative to fix up and improve Date/Time component of WordPress core.
Extension of PHP’s DateTime and DateTimeZone classes for WordPress context.
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.
Here’s what was said about this presentation on social media.
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