WordPress breaks time (and how to fix it)

Andrey “Rarst” Savchenko

• Rarst.net
• WP contractor
• 1 Gs old
• 310 Ms WP

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

1 525 435 200

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();
1525435200
echo $dt->format( DATE_RFC3339 );
2018-05-04T14:00:00+02:00
echo $dt->getTimezone()->getName();
Europe/Berlin

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 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();

date_i18n()

date_i18n() logic

echo date_i18n( 'j. F Y, G.i \U\h\r T' );

1. j. F Y, G.i \U\h\r T
2. j. \M\a\i Y, G.i \U\h\r T — locale
3. j. \M\a\i Y, G.i \U\h\r \C\E\S\T — zone
4. 4. Mai 2018, 14.00 Uhr CEST — date()

date_i18n() fails w/ gmt_offset

echo date_i18n( DATE_RFC3339 );
2018-05-04T14:00:00+02:00

echo date_i18n( DATE_RFC3339 );
2018-05-04T14:00:00+00:00

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

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
			

WpDateTime to wrap date_i18n()

$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
			

post_date

the_date( DATE_RFC3339 );
2018-05-04T13:00:00+01:00

post_date fails w/ changed time zone

the_date( DATE_RFC3339 );
2018-05-04T13:00:00+02:00

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 );
2018-05-04T14:00:00+02:00

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

Thank you for your time! Questions?

Image credits

• Photo by Adina Voicu CC0
• Photo by Eugene Shelestov CC0