fix(post-date): preserve classic theme markup and fix archive titles

[rbcorrales]

All Submissions:

• Have you followed the Newspack Contributing guideline?
• Does your code follow the WordPress' coding standards and VIP Go coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Follow-up to #4579. Addresses review feedback from @laurelfulford about preserving the classic theme's HTML markup for the updated date, and fixes the archive title regression.

• Renamed hook from newspack_theme_after_posted_on to newspack_theme_posted_on (now fires inside newspack_posted_on() in the theme)
• Changed classic theme output to bare inner elements (<span class="updated-label"> + <time class="updated">) matching the old theme markup exactly
• Removed plugin's inline CSS for .updated-date (theme provides .updated-label styling)
• Added in_the_loop() guard to filter_get_the_date to prevent archive titles showing relative dates (e.g. "Daily Archives: 2 days ago")
• Added time.updated[datetime] to the relative-time JS selector so the updated date gets a hover tooltip on classic themes

Requires companion theme PR: Automattic/newspack-theme#2658. Must ship together.

Closes NPPD-1278.

How to test the changes in this Pull Request:

1. Activate the classic Newspack theme (with the companion theme PR) and enable both "Show relative dates" and "Show last updated date" in Newspack > Settings > Advanced Settings > Post Date.
2. Create or find a post modified well after publication (at least 24 hours). Verify the markup is all inside one .posted-on span: <time class="entry-date published"> + <span class="updated-label">Updated </span> + <time class="updated">.
3. Hover over both dates and verify both show a tooltip with the full date.
4. Visit a daily archive page and verify the title shows the full date, not "X days ago".
5. Switch to the block theme. Verify the updated date still renders correctly with data-newspack-modified and wp-block-post-date__modified-date.
6. Open a post in the block editor. Verify the "Hide/Show last updated date" toggle appears in the Summary panel.

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran tests with your changes locally?

[Copilot]

Pull request overview

Adjusts the Post Date feature integration to better match the classic Newspack theme’s historical markup while preventing relative-date formatting from leaking into archive titles.

Changes:

• Switch classic-theme updated-date injection to the new newspack_theme_posted_on hook and adjust classic updated-date HTML output to match legacy markup.
• Prevent get_the_date “time ago” conversion from applying outside the loop (fixes archive title regressions).
• Update the relative-time JS to also target time.updated[datetime] and remove the plugin’s classic updated-date inline CSS.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 5 comments.

File	Description
includes/class-post-date.php	Renames the classic-theme hook, updates classic updated-date markup, removes inline CSS, and adds an in_the_loop() guard in get_the_date filtering.
src/other-scripts/relative-time/index.js	Expands the selector to include time.updated[datetime] so classic updated dates get tooltips/updates.
tests/unit-tests/class-post-date-test.php	Updates the get_the_date filter test to simulate being “in the loop”.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.