Proposal: Add On This Day Widget - #11630

Summary

Adds a new On This Day dashboard widget to WordPress core that surfaces the current user's posts published on today's month and day in previous years, so returning authors see a friendly nudge of what they wrote one, five, or ten years ago.

The widget is implemented as a first-class core feature, following the same pattern as Site Health.

User-facing behavior

• Widget title reads On This Day · <Month Day> and appears in the dashboard grid for users with edit_posts.
• Each year is shown with a year badge (e.g. 2023 · 3 yrs) and the posts published that day as cards with excerpt, time, categories, and Edit/View links.
• Draft and private posts are included for the author and visually distinguished; public posts link to the edit screen with a View link to the permalink.
• Empty state messaging encourages the author when today has no historical posts.

Screenshots

Testing

• Checkout this PR locally and run npm run env:start, then npm run env:install.
• Go to Dashboard (admin:password), you should see the widget.
• Insepect its empty state.
• Import this file to create backdated posts: filexml
• Use the widget.

Trac ticket: https://core.trac.wordpress.org/ticket/65116#ticket

Use of AI Tools

AI assistance: Yes
Tool(s): Cursor
Model(s): Claude Opus 4.7 + Codex 5.5
Used for: The code is ~50% written with AI, but I guided it every step of the way and reviewed every line.

This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.