CalendarLint
Compatibility

Why the same ICS file looks different in each calendar app

A practical look at differences that are documented, verified, or inferred.

CalendarLint EditorialUpdated 10 min read
Applies to: Google Calendar, Apple Calendar, Outlook
team-calendar.icsOne calendar file
Import
One-time copyEvents stay as they were on import day
Subscribe
Connected calendarYour calendar checks the source for updates
Importing copies events once. Subscribing keeps a separate calendar connected to its source.
On this page
The short answerWhat you may noticeThe most common causesA minimal ICS exampleHow to check itBefore you import again

The short answer

Importing an ICS file copies the events into a calendar once. Subscribing adds a separate calendar that can check its source for changes. If you expect future updates, use a subscription when the publisher provides a calendar URL.

The two actions can look similar at first. The difference becomes visible later: an imported event does not know where its original file came from.

What you may notice

  • A changed event still shows its old time.
  • New events never appear in the imported calendar.
  • Importing the file again creates duplicates.

The most common causes

The file was downloaded instead of subscribed to

A downloaded .ics file is a snapshot. Opening it usually starts an import flow, even when the website calls it a “calendar link.”

The calendar URL is no longer reachable

A subscription depends on a stable URL. Authentication, redirects, or a removed feed can stop updates.

A minimal ICS example

The example below is fictional and contains no real calendar data.

1BEGIN:VCALENDAR
2VERSION:2.0
3BEGIN:VEVENT
4UID:design-review@example.test
5DTSTART:20261104T150000Z
6SUMMARY:Design review
7END:VEVENT
8END:VCALENDAR

How to check it in CalendarLint

  1. Open the file in ICS Viewer.
  2. Confirm the event count and intended dates.
  3. Open an event to review its UID and written time.
  4. Compare the file with a newer download if updates are missing.

Before you import the file again

  • Confirm whether you need a one-time copy or ongoing updates.
  • Remove the earlier import if importing again would create duplicates.
  • Use a test calendar when the file contains many events.

Sources
RFC 5545 iCalendar specification · Platform documentation should be checked for the calendar app and version you use.

Continue reading

Related calendar guides

ICS BasicsImporting vs. subscribing to an ICS calendarTime ZonesWhy is my ICS event one hour early or late?TroubleshootingWhy won’t my ICS file import?