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·LeaveSync Team

ICS feeds explained

What an ICS calendar feed is, how LeaveSync generates them, and how to subscribe in Outlook, Google Calendar, and Apple Calendar.

What is an ICS feed?

An ICS feed (also called a calendar subscription or iCalendar feed) is a URL that calendar applications can subscribe to. When the data behind the URL changes, the calendar app fetches a fresh copy and updates the events it shows.

The format is standardised in RFC 5545. Every major calendar application supports it: Outlook, Google Calendar, Apple Calendar, and many others.

How LeaveSync generates feeds

LeaveSync generates one ICS feed per person. The feed contains that person's:

  • Approved leave synced from Xero Payroll
  • Manual availability entries (WFH, travelling, training, client site)
  • Events filtered by the privacy rules configured by the administrator

Feeds are generated at request time and cached. When leave is approved, declined, or cancelled, the cache is invalidated and the feed is regenerated on the next request.

Stable event UIDs

Each event in the feed has a stable, deterministic UID. This ensures that when leave is updated (for example, dates are changed), the calendar app updates the existing event rather than creating a duplicate.

UIDs are generated from a combination of the person ID, the availability record ID, and the feed ID. They are consistent across cache invalidations and token regenerations.

Secure token URLs

Feed URLs are not guessable. Each URL contains a signed token that is specific to the person and the feed configuration. If a URL is shared outside the intended audience, the token can be revoked and regenerated. Existing calendar subscriptions using the old URL will stop receiving updates.

Tokens are never stored in plaintext. Only a cryptographic hash is persisted.

Subscribing in your calendar app

Outlook (desktop or web)

  1. Open Calendar.
  2. Select Add calendar and then Subscribe from web.
  3. Paste the ICS feed URL and select Import.

Google Calendar

  1. Open calendar.google.com.
  2. Click the + next to Other calendars and select From URL.
  3. Paste the ICS feed URL and click Add calendar.

Note: Google Calendar refreshes subscribed calendars every 12 to 24 hours.

Apple Calendar

  1. Open Calendar on Mac.
  2. Go to File and select New Calendar Subscription.
  3. Paste the ICS feed URL and click Subscribe.
  4. Configure the refresh interval (every hour is recommended).