WordPress breaks time (and how to fix it)

Andrey “Rarst” Savchenko

• Rarst.net
• WP contractor
• 1 Gs old
• 325 Ms WP
• Date/Time maintainer

Had you ever...

changed WP time zone?

Settings → General → Timezone

Had you ever...

output localized time?

date_i18n(), the_date(), etc.

A very brief history of time

1. solar time
2. city time
3. rail time
4. time zones
5. Universal Coordinated Time

Unix time

1 540 645 200

seconds since 1970–01–01 00:00:00 UTC

Unix time

• consistent
• storage–friendly
• comparison–friendly
• not human readable

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 DateTime

• UTC–based
• formatting
• parsing
• primarily English

WP time

• PHP 4 code
• partial PHP 5 retrofit
• custom time zone logic
• custom internationalization

WpDateTime

• extends PHP DateTime classes
• works around WP bugs
• parses WP data

wp_date (work in progress...)

• core bugs audit & fixes
• unified timezone processing
• real timestamps & canonical UTC

WP time zone options

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+)

WpDateTimeZone to parse time zone

$timezone = WpDateTimeZone::getWpTimezone();

Hopefully in wp_date: wp_timezone()

date_i18n()

Hopefully in wp_date: wp_date()

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()

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

post_date

the_date( DATE_RFC3339 );
2018-10-27T14:00:00+01:00

post_date fails w/ changed time zone

the_date( DATE_RFC3339 );
2018-10-27T14:00:00+03:00

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

WpDateTime to parse post date

$time = WpDateTime::createFromPost( get_post() );
echo $time->formatI18n( DATE_RFC3339 );
2018-10-27T16:00:00+03:00

Hopefully in wp_date: canonical UTC.

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

Thank you for your time! Questions?

Image credits

• Photo by Adina Voicu CC0
• “Time” comic by Zach Weinersmith
• Photo by Eugene Shelestov CC0