ics.js - HaoTian's fork

What is added to the original ics.js:

• Better compatibility for recurring events
• Add reminder functionality for events (valarms)
• Add support for timezones
• Add support for geo location and Apple Calendar's map integration

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A browser friendly .ics/.vcs file generator written entirely in JavaScript!

Now you can make calendar friendly files client-side. It outputs .ics files, so the files are compatible with all modern calendar software (Outlook, Apple Calendar, Google, etc.)

How To Use

Simply invoke the object and use the functions...

var cal = ics(uidDomain, prodId, vtimezone);
cal.addEvent(subject, description, location, begin, end, rrule, alarmBefore, geo, appleGeo);
cal.addEvent(subject, description, location, begin, end); // yes, you can have multiple events :-)
cal.download(filename);

All addEvent parameters after stop are optional:

• rrule : Recurrence rule object (see Recurring Events below)
• alarmBefore : Number of minutes before the event to trigger a reminder notification
• geo : Object with lat, lon, and optional radius (in metres) for a GEO field
• appleGeo : Object with lat and lon to override the Apple Maps pin location (falls back to geo if omitted)

begin and end need to be formatted in a way that is friendly to Date()

uidDomain sets the domain part of each event's UID. prodId is the calendar product name. vtimezone is an optional VTIMEZONE block string; when provided, DTSTART/DTEND are emitted with a TZID parameter instead of floating time.

Recurring Events

Recurring events can be added with the rrule object.

cal.addEvent(subject, description, location, begin, end, rrule)

The rrule object has the following properties:

• freq : Required. The frequency of event recurrence. Can be DAILY, WEEKLY, MONTHLY, or YEARLY.
• until : A date string representing the date on which to end repitition. Must be friendly to Date()
• count : Alternative to until. Repeat the event count times. Must be an integer
• interval : The interval of freq to recur at. For example, if freq is WEEKLY and interval is 2, the event will repeat every 2 weeks. Must be an integer.
• byday : Which days of the week the event is to occur. An array containing any of SU, MO, TU, WE, TH, FR, SA.

The four properties described above are not exhaustive of recurrence rule capabilities. If extra functionality is required, you can set the rrule.rule property to a full recurrence rule string. In this case, none of the four properties described above are necessary. See this page for a description of recurrence rules.

Example

• Demo

<script>
  // Basic usage (no timezone)
  var cal = ics();
  cal.addEvent('All Day Event', 'This is an all day event', 'Nome, AK', '8/7/2026', '8/7/2026');
  cal.addEvent('Thirty Minute Event', 'This is a thirty minute event', 'Nome, AK', '8/7/2026 5:30 pm', '8/7/2026 6:00 pm');

  // With timezone
  var SEP = (navigator.appVersion.indexOf('Win') !== -1) ? '\r\n' : '\n';
  var vtimezone = [
    'X-WR-TIMEZONE:America/New_York',
    'BEGIN:VTIMEZONE',
    'TZID:America/New_York',
    'BEGIN:STANDARD',
    'DTSTART:19701101T020000',
    'TZOFFSETFROM:-0400',
    'TZOFFSETTO:-0500',
    'TZNAME:EST',
    'END:STANDARD',
    'END:VTIMEZONE'
  ].join(SEP);

  var tzCal = ics('myapp.example', 'My Calendar', vtimezone);

  // Recurring weekly event with a 15-minute reminder
  tzCal.addEvent(
    'Stand-up',
    'Daily stand-up meeting',
    'Office',
    '2026-03-02 09:00',
    '2026-03-02 09:30',
    { freq: 'WEEKLY', byday: ['MO', 'TU', 'WE', 'TH', 'FR'], until: '2026-12-31' },
    15
  );

  // Event with geo coordinates and Apple Maps integration
  tzCal.addEvent(
    'Conference',
    'Annual developer conference',
    'Moscone Center, San Francisco, CA',
    '2026-06-10 09:00',
    '2026-06-10 18:00',
    null,
    null,
    { lat: 37.7844, lon: -122.4000, radius: 100 },
    { lat: 37.7844, lon: -122.4000 }
  );

  tzCal.download('my-calendar');
</script>
<a href="javascript:tzCal.download('my-calendar')">Download Calendar</a>

Dependencies

The tool uses 2 libraries from the following projects:

• FileSaver.js
• Blob.js

I've compressed them and included them into the source for the normal file. Other variations are available in the repo.

If you want IE to allow for either opening documents as well as saving documents, you can use my fork of FileSaver.js (https://github.com/nwcell/FileSaver.js)... Though you honestly are probebly best off using their main.

Supported Browsers

Browser	Dependancies
Firefox 20+	FileSaver.js
Firefox ≤ 19	FileSaver.js, Blob.js
Chrome	FileSaver.js
Chrome for Android v28+	FileSaver.js
IE 10+	FileSaver.js
Opera Next	FileSaver.js
Opera < 15	FileSaver.js, Blob.js
Safari ≤ 6	FileSaver.js, Blob.js

Credits

• Travis Krause: Me
• Kyle Hornberg: Added multi event functionality and made everything a package firendly