Nextcloud version (eg, 20.0.5): 20.0.7
Operating system and version (eg, Ubuntu 20.04): Linux 4.19.0-13-amd64 x86_64 / Debian 10.7 / YunoHost 126.96.36.199 (stable)
Apache or nginx version (eg, Apache 2.4.25): nginx version?
PHP version (eg, 7.4): 7.3.29
The issue you are facing:
Is this the first time you’ve seen this error? (Y/N): Y
Steps to replicate it:
Go to Agenda and set on week mode to see the number of the week in the current year. Note the number of one week.
Go to Event app. Go to the adding slot page to manage availabilities. Choose the same week (with the dates) on the date field → the number of the week is different (+1 in the Event app). The good one is the Agenda app one.
PS : Sorry but impossible to load screenshots to illustrate