feat: On This Day — release anniversaries and collection calendar

[SimplicityGuy]

Overview

Surface time-aware content from the knowledge graph: release anniversaries, historical milestones, and "on this day" moments. "30 years ago today, Endtroducing was released." "This week marks the anniversary of 47 releases in your collection."

Low implementation cost since release year data already exists on masters and releases in the graph. High engagement value — gives users a reason to open the app daily.

Proposed Endpoints

API Endpoints (api/routers/calendar.py)

Endpoint	Description
GET /api/calendar/today	Releases with anniversaries today (all data + user's collection)
GET /api/calendar/week	Upcoming anniversaries this week
GET /api/calendar/month/{year}/{month}	Calendar view of release anniversaries for a given month
GET /api/calendar/milestones	Notable upcoming milestones: 10th, 25th, 50th anniversaries
GET /api/calendar/history/{month}/{day}	"On this day in music" — notable releases across all years

Query Parameters (shared)

• collection_only=true — filter to only the authenticated user's collection
• genre={style} — filter by genre/style
• milestone_years=10,25,50 — which anniversary years to highlight

Response Shape (example: today)

{
  "date": "2026-03-18",
  "anniversaries": [
    {
      "release_id": 789,
      "title": "Endtroducing.....",
      "artist": "DJ Shadow",
      "year": 1996,
      "years_ago": 30,
      "milestone": true,
      "in_collection": true,
      "label": "Mo' Wax"
    }
  ],
  "stats": {
    "total_anniversaries": 142,
    "collection_anniversaries": 12,
    "milestones": 3
  }
}

Data Notes

• Discogs masters/releases have a year field but not always exact month/day
• For releases with only a year, distribute them across the year or show them in a "this year" section
• Releases with full dates (from release notes or Discogs released field) get exact day matching
• PostgreSQL release_dates table may be needed to store parsed exact dates when available

Explore UI — "Calendar" Pane

Add a Calendar pane to the Explore sidebar navigation.

Pane Layout

1. Today's Highlights — hero section showing the most notable anniversary today (largest milestone year, most popular release). Card with: release title, artist, "X years ago today", label, year
2. Anniversary Feed — scrollable feed of today's anniversaries, sorted by milestone significance. Each entry shows: release title, artist, years ago, milestone badge (🎂 10yr, 🥈 25yr, 🥇 50yr). Toggle between "All" and "My Collection"
3. This Week — compact list of upcoming anniversaries for the next 7 days
4. Monthly Calendar — grid calendar view (current month) where days are color-coded by number of anniversaries. Clicking a day shows that day's releases. Navigation arrows to browse months
5. Milestone Countdown — upcoming milestone anniversaries in the user's collection: "In 23 days: 25th anniversary of Kid A"

UI Details

• Monthly calendar grid is a simple HTML table styled with the design system
• Day cells show a count badge; clicking expands to a release list below the calendar
• Milestone badges use consistent iconography
• "Collection only" toggle filters all sections simultaneously
• Feed auto-refreshes at midnight (or on pane activation if stale)
• Empty state: "No anniversaries today" with a teaser of the next upcoming one

Integration Points

• Notifier Service (feat: Notifier Service — watchlists and alerts for new music data #86): Anniversary alerts — "Tomorrow is the 25th anniversary of OK Computer in your collection"
• Webhook/Event Stream (feat: Webhook / Event Stream — real-time notifications for integrations #102): Daily anniversary digest as a webhook event
• Dashboard (feat: Admin Dashboard — operational visibility and historical metrics #104): "Today in music" widget for the admin dashboard
• Insights (feat: Insights Service — precomputed analytics and music trends #85): Anniversary trends — "March is your biggest anniversary month"

Implementation Notes

• Core query is simple: match releases where year = current_year - N, optionally filtered by collection membership
• For exact date matching, parse the released field from Discogs data (format varies: "1996-11-19", "1996", "November 1996")
• Precompute daily anniversaries via a scheduled task and cache in Redis (TTL 24h, refreshed at midnight)
• Month/day extraction from partial dates: if only year is known, flag as "year-only" and show in a monthly summary rather than a specific day
• Lightweight feature — minimal new infrastructure needed

Acceptance Criteria

• Today endpoint returns releases with anniversaries on the current date
• Week endpoint returns upcoming 7 days of anniversaries
• Month endpoint returns calendar data for a given month
• Milestones endpoint highlights 10th, 25th, and 50th anniversaries
• Collection-only filter works across all endpoints
• Explore UI "Calendar" pane displays all sections
• Exact date parsing handles Discogs date format variations gracefully
• Daily anniversary cache refreshed automatically
• ≥80% test coverage

[SimplicityGuy]

Status update — backend exists, no user-facing feature

Anniversary computation is implemented in the insights pipeline:

• api/routers/insights_compute.py — GET /api/internal/insights/anniversaries endpoint
• api/queries/insights_neo4j_queries.py — query_monthly_anniversaries() with configurable milestone years (25, 30, 40, 50, 75, 100)
• Consumed internally by the Insights service for precomputation

However, this is an internal API endpoint — there is no user-facing "On This Day" feature, calendar UI, or public endpoint exposing anniversary data. The issue's proposed UI features (calendar view, daily highlights, collection-specific anniversaries) are not implemented.

[SimplicityGuy]

Status Update — 2026-03-25

Not started. No implementation or design work has been merged to main for this feature.