Shared calendar between etar and thunderbird results in etar displaying entry at wrong time

[grrrrr]

Setup

I have the following set up

• etar 1.0.30 (f-droid) on android phone
• davX5 4.2.4-ose (f-droid) on android phone
• thunderbird/lightning 102.3.1 on fedora
• Radicale 3.1.5 on debian

Timezone on phone is set to "region UK / Detect time zone automatically" Timezone on computer is set to Europe/London Timezone on server is set to Europe/London

syncing happens as such etar <--> davX5 <--> radicale <--> thunderbird

Problem description

I can create an entry in etar and it will sync successfully to Thunderbird. The problem arises when I either:

1. Create an entry on Thunderbird's lightning
2. edit a calendar entry in Thunderbird that was created with etar

In Thunderbird the calendar entry displays correctly but once Etar/davx5 syncs it it from the radical server, etar displays the entry with the incorrect time. typically 23:00 the day before.

Example calendar entries

• As I test, I created a calendar entry on the phone with etar.
• The entry with start: 08:00, end: 09:00, date: 2022-11-17 and entry summary of Etar added - this displays in etar at the desired time / date
• I synced the entry to Thunderbird - this displays in Thunderbird at the desired time / date
• On Thunderbird, I edited the entry adding a description of TB edited - - this displays in Thunderbird at the desired time / date
• I synced the updated entry to etar - in etar the entry now is listed as start: 23:00, end: 23:00, date: 2022-11-16

Similar behavior is noted if I create an entry in Thunderbird / Lightning, once it's synced to etar it displays as 23:00 on the day before

Entry copied from radical server after it was created by Etar

BEGIN:VCALENDAR
VERSION:2.0
PRODID:DAVx5/4.2.4-ose ical4j/3.2.5 (ws.xsoh.etar)
BEGIN:VTIMEZONE
TZID:Europe/London
LAST-MODIFIED:20220816T024022Z
BEGIN:STANDARD
DTSTART:19961027T020000
RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU
TZNAME:GMT
TZOFFSETFROM:+0100
TZOFFSETTO:+0000
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:19810329T010000
RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU
TZNAME:BST
TZOFFSETFROM:+0000
TZOFFSETTO:+0100
END:DAYLIGHT
END:VTIMEZONE
BEGIN:VEVENT
UID:87958746-0cea-49a9-9438-4fa99887101e
DTSTART;TZID=Europe/London:20221117T080000
DTEND;TZID=Europe/London:20221117T090000
DTSTAMP:20221109T162325Z
STATUS:CONFIRMED
SUMMARY:Etar added
END:VEVENT
END:VCALENDAR

The same entry copied from the radical server after a small edit was made via Thunderbird

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Mozilla.org/NONSGML Mozilla Calendar V1.1//EN
BEGIN:VTIMEZONE
TZID:Europe/London
BEGIN:STANDARD
DTSTART:19700329T010000
RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU
TZNAME:BST
TZOFFSETFROM:+0000
TZOFFSETTO:+0100
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:19701025T020000
RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU
TZNAME:GMT
TZOFFSETFROM:+0100
TZOFFSETTO:+0000
END:DAYLIGHT
END:VTIMEZONE
BEGIN:VEVENT
UID:87958746-0cea-49a9-9438-4fa99887101e
DTSTART;TZID=Europe/London:20221117T080000
DTEND;TZID=Europe/London:20221117T090000
DESCRIPTION;ALTREP="data:text/html,%3Cbody%3ETB%20edited%3C%2Fbody%3E":TB e
 dited
DTSTAMP:20221109T162419Z
LAST-MODIFIED:20221109T162419Z
STATUS:CONFIRMED
SUMMARY:Etar added
X-MOZ-GENERATION:1
END:VEVENT
END:VCALENDAR

[benklaasen]

Thanks for logging this, @grrrrr . I have exactly the same problem with Etar 1.0.34 (and the Etar-derived "Calendar" app provided with e.foundation's /e/ OS) and a self-hosted Nextcloud 25.0.3 instance.

A calendar entry created on my wife's Android phone with Tibor Kaputa's "Simple Calendar" is synched to Nextcloud, where it shows up correctly on the Nextcloud Calendar app. Synched in turn to Etar on my /e/ phone, the event shows up as starting and finishing at 23:00 on the previous day.

We're in Ireland, where it's Winter Time now, GMT+0. My phone's timezone is provided by the network, GMT+0. The system time on the Nextcloud server (Ubuntu 20.04) is in GMT+0.