Events without time (end = start) not getting synced from server to device

[titibandit]

Hello,
i'm having an issue where I create a calendar event on my device using simple mobile tools (https://f-droid.org/en/packages/com.simplemobiletools.calendar.pro/), and get it synced to my caldav server using davx5. When syncing again, from server to device, most of the time (but not all the time), the event would not get synced back to the device.
However, when syncing the events to my computer using vdirsyncer (https://github.com/pimutils/vdirsyncer), the event would get through to my computer, meaning that it is indeed present on the server.

One such incriminated event (that gets synced to my computer using vdirsyncer but not to my android device using davx5) would be:
(That's the content of the .ics file as I get it from vdirsyncer)

BEGIN:VCALENDAR
VERSION:2.0
PRODID:DAVx5/4.3.15-ose ical4j/3.2.14 (com.simplemobiletools.calendar.pro)
BEGIN:VTIMEZONE
TZID:Europe/Berlin
LAST-MODIFIED:20230104T023643Z
BEGIN:DAYLIGHT
TZNAME:CEST
TZOFFSETFROM:+0100
TZOFFSETTO:+0200
DTSTART:19810329T020000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=3
END:DAYLIGHT
BEGIN:STANDARD
TZNAME:CET
TZOFFSETFROM:+0200
TZOFFSETTO:+0100
DTSTART:19961027T030000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
END:STANDARD
END:VTIMEZONE
BEGIN:VEVENT
DTSTAMP:20240423T075126Z
UID:a4af5da8-9a92-4665-be26-5a9993c31178
SUMMARY:Geburtsanmeldung
LOCATION:Uniklinik
DTSTART;TZID=Europe/Berlin:20240527T140000
DTEND;TZID=Europe/Berlin:20240527T140000
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR

That would be the content of one event that indeed gets synced back to the device:

BEGIN:VCALENDAR
VERSION:2.0
PRODID:DAVx5/4.3.15-ose ical4j/3.2.14 (com.simplemobiletools.calendar.pro)
BEGIN:VTIMEZONE
TZID:Europe/Berlin
LAST-MODIFIED:20230104T023643Z
BEGIN:DAYLIGHT
TZNAME:CEST
TZOFFSETFROM:+0100
TZOFFSETTO:+0200
DTSTART:19810329T020000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=3
END:DAYLIGHT
BEGIN:STANDARD
TZNAME:CET
TZOFFSETFROM:+0200
TZOFFSETTO:+0100
DTSTART:19961027T030000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
END:STANDARD
END:VTIMEZONE
BEGIN:VEVENT
DTSTAMP:20240408T173251Z
UID:0fdfa0a6-8104-4a80-878b-d999ced88991
SUMMARY:Geburtsanmeldung
LOCATION:Heilig Geist
DTSTART;TZID=Europe/Berlin:20240522T110000
DTEND;TZID=Europe/Berlin:20240522T120000
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR

---

As I'm writing this, I notice that the difference is that in the case of the event that doesn't sync back, it has the same start and end time. This is actually how the calendar app is by default when creating an event: is sets the begin and end times to the same time.
Is this expected behavior?
Cheers.

[rfc2822]

Regarding the first VEVENT:

DTSTART;TZID=Europe/Berlin:20240527T140000
DTEND;TZID=Europe/Berlin:20240527T140000

This event occupies 0 seconds of your time. Maybe that's the reason why the calendar app doesn't show it? At least this is what I have experienced from some calendar apps.

Note that it's specified that an event without DTEND is the same as an event with equal DTSTART and DTEND (when date-time):

For cases where a "VEVENT" calendar component specifies a "DTSTART" property with a DATE-TIME value type but no "DTEND" property, the event ends on the same calendar date and time of day specified by the "DTSTART" property.

So I guess that the calendar app:

• create events with DTSTART and without DTEND locally and shows such events, but
• doesn't show received events with equal DTSTART and DTEND (although that's by definition the same as an event without DTEND)

---

In the second VEVENT, DTSTART is not DTEND, so there's no problem.

[titibandit]

So I guess that the calendar app:

* create events with DTSTART and without DTEND locally and shows such events, but

* doesn't show received events with equal DTSTART and DTEND (although that's by definition the same as an event without DTEND)

So you mean by that, that in that case, Davx5 adds the DTEND being equal to DTSTART in the case it received an event with only DTSTART?

That would make sense.

[rfc2822]

Yes, it makes the implicit thing (missing DTEND means equals to DTSTART) explicit.

[titibandit]

So I've opened an issue (FossifyOrg/Calendar#223) on Fossify calendar bug tracker (where I posted a screencast of the issue for reference). They suggested trying with another app, which I did with the Etar calendar app, and there, exactly the same happens...
This would hint that it indeed is an issue an Davx5's side, as two different calendar app behave exactly the same way.

[rfc2822]

Yes, I have also experienced that multiple calendars don't show events with 0 seconds.

If you however create an event with Etar, they don't have 0 seconds by default and are thus shown. The key is not to view the events with another app, but to create them with another app.

[titibandit]

But as with Fossify Calendar, if you make it zero seconds, the event is initially displayed. It's after a synchronization through davx5 that it disappears. So exactly same behavior here.

The key is not to view the events with another app, but to create them with another app.

I'm not sure I understand that.

[titibandit]

I'm gonna write this message in both the trackers of Fossify Calendar and Davx5, as both sides think the other is at fault (and both sides might be right, or both wrong I don't know :o) )

I don't know which side is more "wrong" and thus where a solution should be deployed, but this behavior is clearly not expected and not ideal. I haven't taken the time to debug this more thoroughly, but the behavior is very predictable and reproducible.
A very obvious workaround is to not make events that last 0 seconds, but some other people are bound to fall in that trap, especially since Fossify cal's default duration for events is actually 0 hours if I'm not mistaken.

[ArnyminerZ]

Please, can you tell us which CalDAV server are you using? It seems to work fine with whatever I use, so it makes me think that the problem may come from the server.

[titibandit]

I am using whatever CalDav server purelymail deploys ... (https://purelymail.com/). So I don't really know. The owner has an issue tracker here: https://github.com/ScottPeterJohnson/purelymail-issues
But what would speak against the server being the culprit, is that when I use vdirsyncer so sync events on my computer, they are indeed here.

[rfc2822]

I assume that vdirsycner uses PROPFIND (to sync all entries), where DAVx5 by default uses REPORT to only sync the events of the last 90 days + the ones in the future.

Can you try to

• set the Past event time limit to no value,
• then again create an event without end time (= with end time same as start time)
• and look whether it disappears?

[rfc2822]

I have reproduced the problem and it's a server problem – it doesn't send the event over REPORT calendar-query (only over PROPFIND, as I have assumed.

Can you report that to Purelymail?

[titibandit]

Hello, indeed setting Past event time limit to no value make those 0 seconds event sync now.
Yes I can report that to Purelymail. I can mainly link this discussion, as I'm myself not familiar with the actual issue that's going on behind the scene.
Thanks for your time again.