iCal - all day events lasting one day are recognized for the day before

DFS-90

Hello,

I got a weird problem concerning the ICS calendar platform and all day events that last one single day. I managed to connect my Kopano calendar to HomeAssistant via SSL (Let’s encrypt).

Everything else works fine:

umlauts
all day events that last two or more days
events that last a certain period of time, e. g. 8 am to 7 pm

As soon as I create an all day event that lasts one day, it is recognized for the day before.

Example:

event is created for 2022/09/11, all day
my mobile phone recognizes that event for 2022/09/11, all day
Kopano WebApp recognizes that event for 2022/09/11, all day
HomeAssistant recognizes that event for 2022/09/10, all day

This is an excerpt from the .ics-file:

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Kopano//11.0.2//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
TRANSP:TRANSPARENT
X-MICROSOFT-CDO-INTENDEDSTATUS:FREE
CREATED:20220907T230853Z
LAST-MODIFIED:20220907T230901Z
DTSTAMP:20220907T230901Z
DTSTART;VALUE=DATE:20220910
DTEND;VALUE=DATE:20220911
SUMMARY:Test WebApp ganztÃ¤gig 11.09.
PRIORITY:5
CLASS:PUBLIC
UID:
040000008200E00074C5B7101A82E008000000008064F3D00EC3D801000000000000000001
 000000C5EA678954DE4A9D840365DFBE14C377
X-MICROSOFT-CDO-OWNER-CRITICAL-CHANGE:20220908T075343Z
X-MICROSOFT-CDO-ATTENDEE-CRITICAL-CHANGE:20220908T075343Z
X-MICROSOFT-CDO-APPT-SEQUENCE:0
X-MICROSOFT-CDO-OWNERAPPTID:-1
X-MICROSOFT-CDO-ALLDAYEVENT:TRUE
END:VEVENT

I also did a second test with an empty calendar for 2022-09-12 to be sure:

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Kopano//11.0.2//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
TRANSP:TRANSPARENT
X-MICROSOFT-CDO-INTENDEDSTATUS:FREE
CREATED:20220908T213511Z
LAST-MODIFIED:20220908T213511Z
DTSTAMP:20220908T213511Z
DTSTART;VALUE=DATE:20220911
DTEND;VALUE=DATE:20220912
SUMMARY:appointment test 2022-09-12\, all day
PRIORITY:5
CLASS:PUBLIC
UID:
 040000008200E00074C5B7101A82E00800000000800564E4CAC3D801000000000000000001
 00000035A1B8102AFD4AE9AC9D0C575AFC4F57
X-MICROSOFT-CDO-OWNER-CRITICAL-CHANGE:20220908T213519Z
X-MICROSOFT-CDO-ATTENDEE-CRITICAL-CHANGE:20220908T213519Z
X-MICROSOFT-CDO-APPT-SEQUENCE:0
X-MICROSOFT-CDO-OWNERAPPTID:-1
X-MICROSOFT-CDO-ALLDAYEVENT:TRUE
END:VEVENT
END:VCALENDAR

The issue happened when trying to connect my Kopano calendar to HomeAssistant (please also see HomeAssistant Forum).

I’ve also tried to switch to kDAV instead of Kopano iCal - same behaviour.
All timezones are set correctly (“Europe/Berlin”).

Does anybody know how to troubleshoot this?

Thanks in advance,
David