Time Zone Issue With Remote Calendar - All Events Are One Hour Off
The Problem
When subscribing to a remote calendar in the same time zone, all events are shown 1 hour late. This issue is particularly puzzling since the time zone of the Home Assistant instance is set to Europe/Zurich, which should align with the time zone specified in the remote calendar's ICS file.
App Provider and Time Zone
The app provider of the remote calendar is app.myice.hockey, and the time zone of the Home Assistant instance is Europe/Zurich. This suggests that the issue is not related to the time zone itself, but rather to how Home Assistant is interpreting the time zone information in the remote calendar's ICS file.
Sample ICS File
The following is a sample ICS file that demonstrates the problem, with the location and summary edited out for privacy:
### Sample ICS File
```yaml
BEGIN:VCALENDAR
PRODID:-//myicehockey//NONSGML v1.0//EN
VERSION:2.0
CALSCALE:GREGORIAN
METHOD:PUBLISH
X-WR-CALNAME:MIH Player
X-WR-CALDESC:MIH Player
X-WR-TIMEZONE:Europe/Zurich
BEGIN:VEVENT
ORGANIZER;CN=MIH:MAILTO:app-no-communication@myice.hockey
UID:PP621883
DTSTAMP:20250519T180000Z
CREATED:20250517T073125
LAST-MODIFIED:20250517T073125
DTSTART:20250519T180000
DTEND:20250519T193000
LOCATION:School sports facility, Zurich
SUMMARY:Off-Ice Training
TRANSP:TRANSPARENT
CATEGORIES:PRACTICES
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
ORGANIZER;CN=MIH:MAILTO:app-no-communication@myice.hockey
UID:PP622295
DTSTAMP:20250522T193000Z
CREATED:20250517T073125
LAST-MODIFIED:20250517T073125
DTSTART:20250522T193000
DTEND:20250522T203000
LOCATION:Ice Rink Zurich
SUMMARY:TRAINING
TRANSP:TRANSPARENT
CATEGORIES:PRACTICES
CLASS:PUBLIC
END:VEVENT
Faulty DTSTAMP Entry
The DTSTAMP entry in the ICS file appears to be faulty, as it is set to the future and has the same value as the event, but in UTC. This would result in a two-hour offset, which is likely contributing to the issue.
DTSTART Entry
The DTSTART entry, however, looks okay, as it is a local time without an additional time zone qualifier. This means that it should normally be assumed to be in the Europe/Zurich time zone, which is the same time zone as Home Assistant.
Related Issue
This issue is likely related to issue #142555 on the Home Assistant GitHub repository.
System Information
What version of Home Assistant Core has the issue?
core-2025.5.2
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
- Remote Calendar
Link to integration documentation on our website
Diagnostics information
- No response
Example YAML snippet
Anything in the logs that might be useful for us?
Additional information
- No response
Conclusion
Q&A
Q: What is the issue with the remote calendar?
A: The issue is that all events are shown 1 hour late when subscribing to a remote calendar in the same time zone.
Q: What is the time zone of the Home Assistant instance?
A: The time zone of the Home Assistant instance is Europe/Zurich.
Q: What is the time zone specified in the remote calendar's ICS file?
A: The time zone specified in the remote calendar's ICS file is also Europe/Zurich.
Q: Why is the issue occurring if the time zones match?
A: The issue is likely related to how Home Assistant is interpreting the time zone information in the remote calendar's ICS file.
Q: Is the DTSTAMP entry in the ICS file faulty?
A: Yes, the DTSTAMP entry in the ICS file appears to be faulty, as it is set to the future and has the same value as the event, but in UTC.
Q: Is the DTSTART entry in the ICS file correct?
A: Yes, the DTSTART entry in the ICS file looks okay, as it is a local time without an additional time zone qualifier.
Q: Is this issue related to any other known issues?
A: Yes, this issue is likely related to issue #142555 on the Home Assistant GitHub repository.
Q: What version of Home Assistant Core has the issue?
A: The issue is present in core-2025.5.2.
Q: What type of installation are you running?
A: The installation is running Home Assistant OS.
Q: Which integration is causing the issue?
A: The Remote Calendar integration is causing the issue.
Q: Where can I find more information about the Remote Calendar integration?
A: You can find more information about the Remote Calendar integration on the Home Assistant website at https://www.home-assistant.io/integrations/remote_calendar.
Q: Are there any additional steps I can take to troubleshoot the issue?
A: Yes, you can try checking the logs for any relevant information, and also try updating to the latest version of Home Assistant Core.
Q: Is there a known solution to the issue?
A: No, there is no known solution to the issue at this time.
Q: Where can I report any additional information or feedback about the issue?
A: You can report any additional information or feedback about the issue on the Home Assistant GitHub repository at https://github.com/home-assistant/core/issues.