Fix timezone in Date block

[westonruter]

Fixes #39984.

The date/time being displayed in the Date block is currently using gmdate():

gutenberg/packages/block-library/src/post-date/index.php

Line 79 in a040815

$formatted_date = gmdate( empty( $attributes['format'] ) ? get_option( 'date_format' ) : $attributes['format'], $post_timestamp );

This is incorrect. For comparison, refer to core's get_post_time() function as used by get_the_date() as used in classic themes. It uses wp_date() as follows:

$time = wp_date( $format, $datetime->getTimestamp(), $gmt ? new DateTimeZone( 'UTC' ) : null );

When the $timezone parameter is not passed to wp_date() then it uses the current timezone as specified in the blog's settings.

Testing

I added a Date block in a row in the Single template in Twenty Twenty-Five:

I also have my timezone set to America/Los Angeles:

The current time for me right now is 22:35 (10:35pm) on August 31st. In the block editor, I see this reflected correctly when showing the template in the block editor:

However, if I view the post on the frontend, I see September 1st, since that is the current date in UTC/GMT:

When I switch to the code in this branch so that wp_date() is used instead, then I see the expected date of August 31st:

[github-actions]

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Co-authored-by: westonruter <westonruter@git.wordpress.org>
Co-authored-by: ockham <bernhard-reiter@git.wordpress.org>
Co-authored-by: carolinan <poena@git.wordpress.org>
Co-authored-by: ryelle <ryelle@git.wordpress.org>

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[github-actions]

Flaky tests detected in 580f81f.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/17368683633
📝 Reported issues:

• [Flaky Test] correctly applies dynamic allowed blocks restrictions #51220 in /test/e2e/specs/editor/plugins/inner-blocks-allowed-blocks.spec.js
• [Flaky Test] should refresh the page when stylesheet loading fails #71135 in /test/e2e/specs/interactivity/router-styles.spec.ts

[ockham]

Makes sense. Thank you for the fix!