Use casesCalendars and apps

Calendars that stay right as plans change.

Per-day counts for the month, every session of a recurring series, and a change feed that tells you what moved.

Real screens from TinyJawns, built on Tailend

Try it in the playground Read the docs

/events/calendar · occurrences=expand · changed_since · /v1/changes · /classes

Oct 12–18Fishtown family calendar

Mon126 freeStory timeToddler gym

Tue159 freeLibrary LEGOSwim

Wed147 freeArt club

Thu188 freeMusic & meNature walk

Fri2210 freeFamily movie

Sat4122 freeStory timeSensory JumpFall fest

Sun2915 freeBird walkYoga

GET /v1/philadelphia/events/calendar?from=2026-10-12&to=2026-10-18Sample shown

The problem

A calendar is only as good as its last sync.

Month views are heavy.Counting a month by loading every event is slow and drifts from the list.
Series hide dates.A weekly class is one row on its page, but a calendar needs every date.
Things move.Times shift and events are cancelled after you have copied them.

How to build it

Month, day, then keep it fresh.

Draw the month from counts

One call returns every date in the window with how many events start that day, how many are free, and counts per category. Zeros included.

Try it in the playground

GET/v1/philadelphia/events/calendar?from=2026-10-05&to=2026-10-07Sample from the API reference

{
  "data": [
    {
      "date": "2026-10-05",
      "count": 41,
      "free_count": 22,
      "categories": {
        "storytime_books": 14,
        "arts_creative": 9,
        "sports_active_play": 6
      }
    },
    {
      "date": "2026-10-06",
      "count": 0,
      "free_count": 0,
      "categories": {}
    },
    {
      "date": "2026-10-07",
      "count": 57,
      "free_count": 31,
      "categories": {
        "storytime_books": 19,
        "music_movement": 8
      }
    }
  ],
  "meta": {
    "metro": "philadelphia",
    "window": {
      "from": "2026-10-05",
      "to": "2026-10-07",
      "timezone": "America/New_York"
    },
    "total": 98
  }
}

Fill a day with every occurrence

List the day with occurrences=expand. Recurring series appear once per date, and the list always matches the day's count.

Try it in the playground

GET/v1/philadelphia/events?from=2026-09-14&to=2026-09-15&occurrences=expandSample, trimmed

{
  "data": [
    {
      "id": "b81a95d2-1d4e-46fd-9cff-322a41e429ad",
      "name": "Toddler Time (Ages 5 and Under)",
      "occurrence": {
        "starts_local": "2026-09-14T09:30:00",
        "starts_at": "2026-09-14T13:30:00.000Z",
        "ends_local": null,
        "index": 0
      }
    },
    {
      "id": "b81a95d2-1d4e-46fd-9cff-322a41e429ad",
      "name": "Toddler Time (Ages 5 and Under)",
      "occurrence": {
        "starts_local": "2026-09-15T09:30:00",
        "starts_at": "2026-09-15T13:30:00.000Z",
        "ends_local": null,
        "index": 1
      }
    }
  ],
  "meta": {
    "count": 2,
    "has_more": false
  }
}

Stay in sync with changes

Poll /v1/changes for what moved since your last sync: a closed kind and the field names that changed. Removals appear too.

Try it in the playground

GET/v1/changes?since=2026-09-10T00:00:00Z&metro=philadelphiaSample from the API reference

{
  "data": [
    {
      "version_id": 18231,
      "listing_id": "2f3c9d4e-3d2b-4b7d-9a3e-1b2c3d4e5f60",
      "slug": "storytime-in-the-park-2026-09-12",
      "type": "event",
      "metro": "philadelphia",
      "changed_at": "2026-09-10T06:12:05Z",
      "kind": "date_changed",
      "fields": [
        "starts_at"
      ]
    }
  ],
  "meta": {
    "limit": 1,
    "count": 1,
    "has_more": false
  }
}

Key fields

What keeps a calendar honest.

count, free_count: Occurrences starting that local date, exactly what the day list returns under the same filters.
categories: Per-day counts by category, for colored dots or a filter row without a second call.
occurrence.index: Position in the series. id plus index names one session, so you can store and update it.
starts_local, timezone: Local wall-clock time in the metro's zone, plus the UTC starts_at for your own math.
changed_since: On /events, /classes, /camps and /places: rows edited after an instant. Delivery is at least once, so upsert by id.
kind, fields: On /v1/changes: date_changed, price_changed, archived and more, with the public field names that changed.
schedule.days, term: On /classes: the weekly days and the term dates. Filter with schedule_day and openings=true.
verified_at: When the source last confirmed the listing. Good for a quiet "confirmed this week" line.