ICS Feed incorrectly reports recurring events

[rgabbo]

Issue Summary

I'm using the ICS Feed app to sync with my calendar but I noticed recurring event are incorrectly shifted of one day. For example in the screenshot provided I have a recurring event on monday that on cal.com is reported to be on tuesday.

Steps to Reproduce

1. add ics feed as calendar provided https://ics.teamup.com/feed/ks4zmyg42imc8dhm3j/0.ics

Any other relevant information. For example, why do you consider this a bug and what did you expect to happen instead?

Actual Results

• The recurring event is reported in cal.com one day ahead

Expected Results

• The event should be synced in the correct day

Evidence

[dosubot]

The issue with recurring events being shifted by one day in the ICS Feed app likely stems from how time zones or daylight saving time adjustments are handled. This could be due to incorrect time zone data, improper handling of daylight saving time changes, or errors in time zone conversions, especially in the context of recurring events.

The @calcom/ics-feed package includes logic to adjust event times based on time zones, which is crucial for recurring events. It's important to ensure that time zone information is correctly applied and that any conversions accurately account for daylight saving time. The package attempts to handle time zones by adding a vtimezone component if missing, which is vital for the correct interpretation of recurring events.

There are also known issues with certain time zones being problematic due to daylight saving time adjustments or other calculations. The package identifies these in the isProblematicTimezone function, which could be contributing to the problem if your events fall into these categories.

To address the issue, verify the time zone settings of your calendar and events, ensuring that vtimezone components are correctly defined and match the intended time zones. This step is essential for the accurate generation of recurring event occurrences and their correct display on the calendar.

Sources

• packages/lib/CalendarService.ts
• packages/app-store/ics-feedcalendar/package.json
• packages/app-store/ics-feedcalendar/lib/CalendarService.ts
• packages/lib/isProblematicTimezone.ts

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