JSON to ICS Converter — From API Export to Calendar File

What JSON shape works

The converter looks for an array of objects. A top-level array is the simplest shape — drop this as events.json and each object becomes one event:

[
  {
    "title": "Team standup",
    "start": "2026-09-05T09:00:00Z",
    "end": "2026-09-05T09:15:00Z",
    "location": "Zoom",
    "description": "Daily 15-minute sync"
  },
  {
    "title": "Design review",
    "start": "2026-09-05T14:00:00Z",
    "end": "2026-09-05T15:00:00Z",
    "location": "Room 4B",
    "description": "Sprint 12 mockups"
  },
  {
    "title": "Office closed",
    "start": "2026-09-07",
    "end": "2026-09-08",
    "location": "",
    "description": "Public holiday — all-day"
  }
]

A wrapper object is fine too. The converter checks keys in this order: events, then items, data, rows — {"events":[...]} is the usual API shape. If none of those match, an object whose only key holds an array — {"calendar":[...]} — is used. An object with extra non-array keys such as count will not be unwrapped. Keys across every object are unioned into a header row in first-seen order, so a later event that adds location still maps correctly; earlier events just get an empty cell for that key.

Nested objects and arrays are not flattened. They are JSON.stringify'd into one cell. That keeps the file honest — you can see the blob in the mapper — but a nested date is not a date the parser can read. Flatten before converting, or pick a different export.

Dates in JSON: ISO 8601 is the one that never breaks

Write datetimes as ISO 8601. 2026-09-05T14:00:00Z and 2026-09-05T14:00:00+01:00 are converted into the calendar timezone you pick in the options. A naive 2026-09-05T14:00 — no Z, no offset — is read as wall-clock time in that timezone. A date-only value like 2026-09-05 has no time, so with “Treat rows without a start time as all-day events” checked (the default) it becomes an all-day event. Those three forms are what the preview will parse cleanly.

Unix timestamps are not auto-detected. A number like 1757080800 lands in the cell as digits; the date parser does not treat it as seconds-since-epoch. Convert in your script first — new Date(ms).toISOString() in JavaScript, or the equivalent in Python — then drop the file here. Same rule for millisecond timestamps and for locale strings like “Sept 5, 2026 2pm”: they might parse, they might not. ISO never argues.

Mapping keys to calendar fields

After the file loads, the converter shows the same column mapper used for CSV and Excel. JSON keys appear as columns — title, start, end, location, and whatever else your objects contain. Auto-detect picks likely matches (Subject / Title, Start Date, Location); you fix anything it misses with the dropdowns. Only a start date is required; a row without a title becomes (untitled event).

If your API uses headline instead of title, or begins_at instead of start, pick those columns from the dropdowns — auto-detect will not. The preview shows the first five events; click “Show all N events” to see the rest, which is where a wrong key or a nested date shows itself. Nothing is written until you click Download.

Where JSON events usually come from

The common case is an API: GET /events returns an array, or a body with an events (or data) key. Save that response as .json and drop it in. Scraped listings — conference programmes, cinema times, sports fixtures — end up in the same shape once a script has walked the page.

Notion and Airtable both export CSV and JSON. CSV is already a first-class input on this site; JSON is now the same converter, so pick whichever export your base actually gives you. A CMS dump of upcoming posts or events is the same idea: an array of records with a title and a date.

Google Calendar API responses are the awkward one. The event list lives in items[], which this converter will find — but each item's start is nested as start.dateTime (or start.date for all-day). That nested object is stringified into one cell, so the mapper cannot treat it as a start date. Flatten in your script so start.dateTime is a top-level string, or export the calendar as CSV instead and use the CSV to ICS converter.

Going the other way

To get events back out of a calendar file, use the ICS to CSV tool. That gives you a spreadsheet. CSV to JSON is then trivial — JSON.stringify on the parsed rows, or any spreadsheet “save as JSON” export. There is no ICS-to-JSON button on this site because CSV is the useful stop in the middle: you can open it, fix dates, and convert either direction from there.

JSON to ICS — FAQ