On This Day

On This Day

Use this skill when the user wants a same-day historical briefing, a source-linked digest, or help building and refining the matching macOS-style web app.

Use on-this-day-bar for the native menu bar app.

Default product shapes:

• a desktop-first web app that feels at home on macOS, with glass panels, a date picker, curated historical cards, strong source linking, and resilient fallback behavior
• a deterministic helper that renders a compact brief or JSON snapshot from the official Wikimedia feed

Quick Start

1. Decide the exact day, timezone, and feed slice the user wants.
2. Prefer the official Wikimedia Feed API endpoint for the day:
   • https://api.wikimedia.org/feed/v1/wikipedia/en/onthisday/all/{MM}/{DD}
3. Run bash scripts/run_on_this_day.sh doctor before editing the web app or checking local preview readiness.
4. Run bash scripts/run_on_this_day.sh inspect before changing apps/on-this-day/.
5. Use bash scripts/run_on_this_day.sh fetch --date 2026-03-27 --type selected --limit 5 for a deterministic local snapshot.
6. Use bash scripts/run_on_this_day.sh run when you need the web app preview server and browser handoff. If the port cannot be bound, the runner falls back to opening index.html directly.
7. If the user wants the native menu bar app, hand them to on-this-day-bar.
8. Return either an on-this-day-brief, a history-day-digest, or an app-refresh-plan, depending on the request.

Accepted Inputs

• a date like 2026-03-27 or a relative date like today
• the user timezone when the date should respect local midnight boundaries
• a slice such as selected, events, births, deaths, or holidays
• a preferred language, with English as the default when none is given
• a limit for how many entries should be shown
• whether the user wants a quick digest, a richer editorial brief, or app changes
• whether the result should favor concise fact cards, links, or visual presentation

Output Artifact

Primary artifacts:

• on-this-day-brief
• history-day-digest
• app-refresh-plan

Default on-this-day-brief sections:

• Date and timezone basis
• Curated entries with years
• Why each entry is interesting now
• Source links

Default history-day-digest sections:

• Day summary
• Selected highlights
• Secondary categories like births, deaths, or holidays
• Editorial note or takeaway
• Source and fallback notes

Default app-refresh-plan sections:

• User-facing goal
• Data source and fetch behavior
• UI changes
• Empty, loading, and error states
• Validation notes

Workflow

Lock The Date First

• Resolve relative dates like today against the user's timezone.
• Use absolute dates in the final output when there is any ambiguity.
• If the request is date-sensitive, say which date you used.

Prefer Official Data

• Use the official Wikimedia Feed API instead of copying facts from arbitrary recap sites.
• Prefer the all feed when building UI so counts and category switching stay in sync.
• Use selected when the user wants a tighter editorial cut.
• Keep links back to the underlying Wikipedia pages whenever possible.

Use The Helper Script When Precision Matters

• Run python3 scripts/fetch_on_this_day.py --date YYYY-MM-DD --type selected --limit 5 for a clean deterministic brief.
• Use --format json when another tool or app needs structured output.
• If selected is empty, the helper script falls back to events and makes that fallback explicit.

Shape The Presentation

• Default to a polished Mac-style reading experience, not a dump of bullets.
• Keep hierarchy clear:
  • date and source confidence first
  • strongest entries next
  • secondary context after that
• Use restrained motion and strong spacing instead of generic card spam.
• Preserve a desktop-first macOS feel when editing the web app in apps/on-this-day/.

Web App Workflow

• Open apps/on-this-day/README.md before editing the browser surface.
• Prefer bash scripts/run_on_this_day.sh run over a manual python3 -m http.server 4173 preview. When the machine cannot bind the preview port, the runner falls back to opening index.html directly.
• Use bash scripts/run_on_this_day.sh fetch --date YYYY-MM-DD --type selected --limit 5 after changing feed logic, date handling, or digest formatting.
• Keep the static app desktop-first and honest about live versus cached data.

Handle Failure Honestly

• If the live feed fails, prefer cached data in the web app and label it clearly.
• If no cached snapshot exists, say the request failed instead of inventing entries.
• Do not paraphrase historical claims as certain if the source could not be fetched.

Mac Product Shapes

• Prefer a polished web app with:
  • faux macOS window chrome
  • Today, previous, next, and random-day navigation
  • a date picker
  • segmented category controls
  • a spotlight card and a scrollable historical timeline
• Keep the main layout readable between 1280 px desktop widths and narrower laptop screens.
• Use local storage for last date, last category, and cached day snapshots so the app feels dependable.

Safety Boundaries

• Do not invent historical facts, dates, or source links.
• Do not attribute a claim to Wikipedia if you did not fetch it from the official feed or linked page.
• Keep present-day commentary separate from historical event text.
• Be careful with violent or tragic entries: keep the tone factual, not sensational.

Example Prompts

• Use $on-this-day to fetch today's official On This Day feed in Singapore and turn it into a polished daily history brief with five entries and source links.
• Use $on-this-day to build a macOS-style day browser that lets me switch between curated events, births, deaths, and holidays for any date.
• Use $on-this-day to give me the most interesting March 27 historical events, explain why they matter, and keep the output grounded in the official Wikimedia feed.
• Use $on-this-day to refine the web app UI, improve empty and error states, and keep the design professional on Mac.

Resources

• scripts/run_on_this_day.sh: local doctor, inspect, fetch, serve, run, and stop helper for apps/on-this-day.
• scripts/fetch_on_this_day.py: deterministic CLI helper for the official On This Day feed
• references/product-spec.md: product family spec, fetch model, fallback states, and visual direction
• references/project-map.md: web app target map, main files, and preview notes
• ../../apps/on-this-day/: the matching web app codebase