[GH-ISSUE #312] Time Zone and "ByDay" confusion #301

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opened 2026-02-25 20:31:22 +03:00 by kerem · 0 comments

kerem commented

2026-02-25 20:31:22 +03:00

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Originally created by @wompydomp on GitHub (May 5, 2021).
Original GitHub issue: https://github.com/aluxnimm/outlookcaldavsynchronizer/issues/312

First of all, thanks everyone for working on this project!

tl;dr: I suspect the BYDAY is not mapped correctly when caldavsync translates an time zones across a day change.

I have an event series in outook (an invite sent to me) that starts in the US (EST time zone) while i am in JST in Japan. I have issues with two events that start for me in the morning (therefore the day before at night in the US). As far as i can tell, CalDav sync is able to adjust the times according the time zone correctly (i tried no time zone settings,create events on server in UTC and create eents on server with downloaded IANA timezones (Asia/Tokyo).

The first day of this series shows up on the correct day/time on my nextcloud server (hosted in Japan). The following events in the series are then mapped to 'a day before' (matching the recurrence of the US time zone).

Below example is downloaded from nextcloud with UTC mapping.

DTEND:20210209T013000Z
DTSTAMP:20210505T045407Z
DTSTART:20210209T010000Z
EXDATE:20210412T010000Z
EXDATE:20210503T010000Z

RRULE:FREQ=WEEKLY;COUNT=17;BYDAY=MO

As you can see above, the byday is set to Monday (which is correct for the US time zone, but not for me in the JST time zone).
The appointment for 2/9 is on the correct date, the next one is on 2/15 (instead of 2/16).

Originally created by @wompydomp on GitHub (May 5, 2021). Original GitHub issue: https://github.com/aluxnimm/outlookcaldavsynchronizer/issues/312 First of all, thanks everyone for working on this project! tl;dr: I suspect the BYDAY is not mapped correctly when caldavsync translates an time zones across a day change. I have an event series in outook (an invite sent to me) that starts in the US (EST time zone) while i am in JST in Japan. I have issues with two events that start for me in the morning (therefore the day before at night in the US). As far as i can tell, CalDav sync is able to adjust the times according the time zone correctly (i tried no time zone settings,create events on server in UTC and create eents on server with downloaded IANA timezones (Asia/Tokyo). The first day of this series shows up on the correct day/time on my nextcloud server (hosted in Japan). The following events in the series are then mapped to 'a day before' (matching the recurrence of the US time zone). Below example is downloaded from nextcloud with UTC mapping. DTEND:20210209T013000Z DTSTAMP:20210505T045407Z DTSTART:20210209T010000Z EXDATE:20210412T010000Z EXDATE:20210503T010000Z RRULE:FREQ=WEEKLY;COUNT=17;BYDAY=MO As you can see above, the byday is set to Monday (which is correct for the US time zone, but not for me in the JST time zone). The appointment for 2/9 is on the correct date, the next one is on 2/15 (instead of 2/16).