Post Date block: Different display when site & user timezone don't match

[ryelle]

Description

I'm in EDT (UTC-4), and I created a post at 12pm. My site is in PDT (UTC-7), so it saved the post as being created at 9:00am PDT. I have a set of post date blocks using different date formats.

In the database, it has

post_date: 2022-04-01 09:00:00
post_date_gmt: 2022-04-01 16:00:00

On the frontend of the site, the Post Date block shows

• ✅ Publish Date (with timezone): Apr 1, 2022 — 9:00 am PDT
• ❌ Publish Date (timestamp): 1648803600
• ✅ Publish Date (ISO 8601): 2022-04-01T09:00:00-07:00

In the site editor, all three formats show different results

• ❌ Publish Date (with timezone): Apr 1, 2022 — 6:00 am PDT
• ❌ Publish Date (timestamp): 1648818000
• ❌ Publish Date (ISO 8601): 2022-04-01T06:00:00-07:00

The timestamp should be 1648828800.

Step-by-step reproduction instructions

1. Set your site to a different timezone than your current TZ
2. Write a post, make note of the publish time
3. Add a Post Date block either to the post, or in the site editor. Use custom format M j, Y — g:i a T to see the full date with timezone.

Screenshots, screen recording, code snippet

Block code used to test, sets up a group with 3 date blocks using different formats.

<!-- wp:group {"style":{"color":{"background":"#ced9c9"}}} -->
<div class="wp-block-group has-background" style="background-color:#ced9c9"><!-- wp:group {"style":{"spacing":{"margin":{"bottom":"12px"}}},"layout":{"type":"flex"}} -->
<div class="wp-block-group" style="margin-bottom:12px"><!-- wp:paragraph -->
<p>Publish Date (with timezone)</p>
<!-- /wp:paragraph -->

<!-- wp:post-date {"format":"M j, Y — g:i a T"} /--></div>
<!-- /wp:group -->

<!-- wp:group {"layout":{"type":"flex"}} -->
<div class="wp-block-group"><!-- wp:paragraph -->
<p>Publish Date (timestamp)</p>
<!-- /wp:paragraph -->

<!-- wp:post-date {"format":"U"} /--></div>
<!-- /wp:group -->

<!-- wp:group {"layout":{"type":"flex"}} -->
<div class="wp-block-group"><!-- wp:paragraph -->
<p>Publish Date (ISO 8601)</p>
<!-- /wp:paragraph -->

<!-- wp:post-date {"format":"c"} /--></div>
<!-- /wp:group --></div>
<!-- /wp:group -->

Environment info

• Gutenberg trunk (12.9)
• WP 5.9.2-alpha-52803
• Theme: Emptytheme
• No other plugins active

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes

[carolinan]

I am able to reproduce this.