Remote Calendar not accepting invalid iCal content from Apple

[ddavis1086]

The problem

I just upgraded to HA 2025.4 and was trying Remote Calendar. I made my calendar public in iCloud and copied the Public Calendar link. I am getting this error: Invalid .ics file

It's probably me but I'm not sure what I'm am doing wrong. Can someone help me?
Thanks

What version of Home Assistant Core has the issue?

core-2025.4.0

What was the last working version of Home Assistant Core?

No response

What type of installation are you running?

Home Assistant OS

Integration causing the issue

No response

Link to integration documentation on our website

No response

Diagnostics information

No response

Example YAML snippet

Anything in the logs that might be useful for us?

Additional information

No response

[home-assistant]

Hey there @Thomas55555, mind taking a look at this issue as it has been labeled with an integration (remote_calendar) you are listed as a code owner for? Thanks!

Code owner commands

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[mib1185]

is there anything in the log?

[edurenye]

This issue does not happen only with the apple calendar, I had the issue with Google calendars also.

And there is the same issue with Office 365 calendars: #142164
And seems to be also the same issue with uploaded file calendars: #136757

In my case, I'm trying to import a public google calendar (https://calendar.google.com/calendar/ical/info%40cvg.cat/public/basic.ics) and I got the error 'Invalid .ics file', if I try to validate using the previously mentioned validator I can't validate because I get this other error "Maximum file size exceeded".

I use this calendar in many places (like Google Calendar or Nextcloud) and works everywhere except here.

Not only that, but I also tried with a private calendar using the Secret address in iCal format and does not work either.

And there is nothing in the logs.

[ddavis1086]

is there anything in the log?

I also do not find anything in the log file about this error.

Dennis

[Frazou1]

Any news about this ? I not able to add public google calendar. Failed to connected

[kcoffau]

+1 iCloud cal.

tried webcam:// and https://

webcal://p60-caldav.icloud.com/published/blablahblah

[allenporter]

For this specific calendar:

https://calendar.google.com/calendar/ical/info%40cvg.cat/public/basic.ics

This calendar is not valid because its not meeting this rule:

The value of the UNTIL rule part MUST have the same value type as the "DTSTART" property.
...
If the "DTSTART" property is specified as a date with UTC
time or a date with local time and time zone reference, then the
UNTIL rule part MUST be specified as a date with UTC time.

Here the is an example where the DTSART is a date time with local time and time zone reference and the UNTIL is a date that is not the same value type.

BEGIN:VEVENT
DTSTART;TZID=Europe/Madrid:20220413T190000
DTEND;TZID=Europe/Madrid:20220413T223000
RRULE:FREQ=WEEKLY;WKST=MO;UNTIL=20221102;BYDAY=WE
...

You'll now get an error like this from the updated logging:

Error reading the calendar information: Failed to parse calendar EVENT component: DTSTART was DATE-TIME but UNTIL was DATE: must be the same value type

[edurenye]

Thanks @allenporter
But what can I do about it? I’ve searched around and found many similar errors, it seems like Google isn’t strictly following the iCalendar specification. As a monopoly, they probably don't care much about adhering to standards, and in a way, this forces us to stick with their ecosystem. For me, if importing Google Calendars doesn’t work (which is what most people use) then this feature becomes useless.

I believe Home Assistant should handle this kind of error more gracefully and continue parsing the file where possible. That said, I suspect the issue lies with the iCalendar parsing library that Home Assistant relies on, rather than with Home Assistant itself. Do you happen to know which library it uses?

In the meantime, I guess we can still fall back on the Google Calendar integration, though I really don’t like having to rely on Google’s APIs just to access a basic calendar feed.

[allenporter]

It will work if you use the Google calendar integration. It has logic to ensure the cleaners are all valid.

[allenporter]

Also to answer your questions: I made the underlying calendar library. This is the same library used by local calendar, and also used in Google calendar.

For local calendar I want it strict so that bugs introduced are caught.

For Google calendar library it rewrites invalid data to be valid while parsing it inside the gcal library.

I don't want to introduce hacks into the upstream library because I like that it is strict and rejects buggy data. Perhaps remote calendar integration can rewrite invalid data if it wants to, though maybe we need to give it hooks to be able to do that.

I hear you that you just want it to work from a user perspective (similar to what Google calendar integration does)

[vidalpascual]

I have the same problem with iCloud calenda. I put the public calendar URL and I get an error.

I have tested: https://p161-caldav.icloud.com/published/2/
and: webcal://p161-caldav.icloud.com/published/2/

And get the same error:

ERROR (MainThread) [homeassistant.components.remote_calendar.config_flow] Error reading the calendar information: Failed to parse calendar contents

:(

[allenporter]

I was able to get an Apple calendar to work following these steps:

1. Navigate to iCloud Calendar web
2. Next to the calendar click the profile looking icon to open Calendar Sharing
3. Turn on Public Calendar
4. Copy the webcal:// link
5. Configure remote calendar with the webcal link

So if you see Failed to parse calendar contents then it means there is a specific thing about the calendar that it is unable to parse and we need additional information to reproduce it. One thing to try can be to enable debug logs to get more detail from the ical library about what it doesn't like. (see https://www.home-assistant.io/docs/configuration/troubleshooting/#debug-logs-and-diagnostics) Another option is to attach the .ics calendar, however, we don't want your personal information here so be careful about doing that. If we have an example .ics that reproduces the problem we can take it from there and see what the problem is.