[BUG] jtxBoard won't set VTIMEZONE components, which violates the iCalendar spec and caused an error in Rustical.

[lzc256]

Describe the bug
Please read previous discussions here: Support for omitted timezone (RFC7809) #172

After updating Rustical to v0.12.1 (which validates the dates more strictly), Rustical returns an HTTP 403 when syncing a newly added task entry.

The author of Rustical figured out that it was a jtxBoard issue:

The issue seems to be that the start and due dates contain timezone references but the corresponding VTIMEZONE components don't exist which is required in the iCalendar spec.

Also, actually before when this error occurs, I found that even if a Timezone is set in jtxBoard, it never worked and the actual Timezone recorded is still UTC.

To Reproduce

1. Navigate to Settings/Tasks Settings
2. Set a Timezone for Set a default {start, due} timezone for tasks.
3. Trigger a sync in DAVx5. The sync will fail and you can see an error in DAVx5 and Rustical.

Expected behavior
VTIMEZONE components are correctly set and the sync succeeds.

Device and version

• Server: Rustical v0.12.1 (Docker Image)

• Client: Android device with jtxBoard(2.14.01-ose) + DAVx5(4.5.7.1-ose).

• Device: Oneplus 13T

• Android version: Android 15

• jtx Board version: 2.14.01-ose

• Downloaded from: F-Droid

[patrickunterwegs]

Thanks @lzc256 for the detailed error description. I need to have a close look at this. Unfortunately this is all a bit complex and probably needs a review of the ical4android library, davx5 and jtx Board. I'll try to fix this soon.

[dilyanpalauzov]

Support for RFC 7809 “Calendaring Extensions to WebDAV (CalDAV): Time Zones by Reference” and stripping timezones from iCalendar objects are two different things. In fact the Cyrus IMAP server (Fastmail) do remove all VTIMEZONEs, when iCalendar objects are uploadod - see strip_vtimezones at https://github.com/cyrusimap/cyrus-imapd/blob/master/imap/caldav_util.c .

For long time I work with iCalendar objects without VTIMEZONE. This works fine with all clients I know. Clients/operating systems are supposed to have their own Olson Timezones database.

In any case jtxBoard could always store dates in UTC. All clients, including jtxBoard, are anyway supposed to convert this to the timezone preferred by the user. Then only for repeating events the timezone has some use, as from it can be extracted the daylight-saving-switch ⇔ When recurring events happen before and after the daylight-saving-switch-date, timezones are necessary and UTC cannot be used. (But it still does not need that timezone definition to be included in the iCalendar object).

Apart from accepting and providing iCalendar objects over CalDAV, what else does Rustical do with these objects? Show them on a webpage, calculate free-busy slots?

In any case https://github.com/lennart-k/rustical says:

Partial RFC 7809 support. RustiCal will accept timezones by reference and handle omitted timezones in objects.