get_post_datetime() always returns local time even when using 'gmt' as $source

[nboole]

This code (below) is copied directly from the github repo at ​https://github.com/WordPress/wordpress-develop/blob/6.2/src/wp-includes/general-template.php#L2793-L2821

<?php
function get_post_datetime( $post = null, $field = 'date', $source = 'local' ) {
        $post = get_post( $post );

        if ( ! $post ) {
                return false;
        }

        $wp_timezone = wp_timezone();

        if ( 'gmt' === $source ) {
                $time     = ( 'modified' === $field ) ? $post->post_modified_gmt : $post->post_date_gmt;
                $timezone = new DateTimeZone( 'UTC' );
        } else {
                $time     = ( 'modified' === $field ) ? $post->post_modified : $post->post_date;
                $timezone = $wp_timezone;
        }

        if ( empty( $time ) || '0000-00-00 00:00:00' === $time ) {
                return false;
        }

        $datetime = date_create_immutable_from_format( 'Y-m-d H:i:s', $time, $timezone );

        if ( false === $datetime ) {
                return false;
        }

        return $datetime->setTimezone( $wp_timezone );
}

In the function above, the variable $wp_timezone is created with the following line: $wp_timezone = wp_timezone(); and it is never modified in the function, which means that $wp_timezone is always the LOCAL timezone for the site.

In the if( 'gmt' === $source) part of the function, the variable $timezone is set based on whether or not the user asked for 'gmt' or 'local' time in the $source parameter.

However, in the return statement, DateTimeImmutable::setTimezone() is called with the variable $wp_timezone rather than using the correctly set variable, $timezone.

This means that get_post_datetime($post, 'date', 'gmt') still returns the WP Local time rather than GMT/UTC time as intended.

The return statement should be re-written to: return $datetime->setTimezone( $timezone );

Changes made to src/wp-includes/general-template.php:
changed return variable in get_post_datetime() from $wp_timezone (which is a timezone object always set to local site time) to $timezone (which is a timezone object set to either GMT/UTC or Local depending on the user's $source parameter)

This should allow the user to request the post_datetime in either local time or gmt time, as intended/expected according to the function's description and params.

Trac ticket: https://core.trac.wordpress.org/ticket/58192

Function changed: get_post_datetime()

Changes made:
Changed function's return statement from return $datetime->setTimezone( $wp_timezone ); to return $datetime->setTimezone( $timezone );

Reasoning for change:
The variable $wp_timezone is a timezone object which is always set to the site's local time. As such, the function get_post_datetime previously ignored the $source parameter, returning site local time even if the $source param was set to 'gmt'

With the change made, the $timezone variable, which is correctly set to either local time or gmt time based on the $source param, should now be returned. That means that get_post_datetime should now correctly take the $source param into account and return the GMT/UTC time when requested by the user.

Trac ticket: https://core.trac.wordpress.org/ticket/58192

…'gmt' as $source

return the gmt/local timezone

Trac ticket:

[Rarst]

Return in local time is intended and documented behavior for the function. There are options for input to instantiate from, but the output is always given in a consistent state and not meant to be configured (this reduces complexity of arguments and room for error). If UTC time is needed, it can be derived from the resulting object.

Thanks for the PR! Closing for now as per https://core.trac.wordpress.org/ticket/58192#comment:4.

Thanks for the PR! Closing for now as per https://core.trac.wordpress.org/ticket/58192#comment:4.