Dummy update possibly shifting time of recurring event

[ymyinfinity]

OGcalsync_2025-12-23.log

Describe the bug

A recurring entry on my calendar shifted to an hour earlier, for all of the recurrences.

Steps to reproduce

1. Add recurring entry to calendar, wait.

Expected behavior

Expect recurring entry to stay at same time slot.

Actual behavior

Upon viewing logs, seeing that recurring meeting stays at same time slot for multiple days, and on one day abruptly shifts to an hour earlier, during a dummy update event.

Setup

see sanitized logs

[2403905]

@ymyinfinity The OCIS does'n have a calendar. I assumed it is an Owncloud 10 issue.

[DeepDiver1975]

Calendaring data is untouched by owncloud - the data is output just like the data is on input.

Where do you observe the time shift besides outlook? owncloud calendar webui? anyother caldav client?

1 hour timeshift could be related to daylight saving .....