Timezone Issue with meeting invitations

We have an issue with the timezones. We are running the Meeting application 1.8 and if we send invitation for meetings, they are always two ours late (UTC instead of CEST, perhaps). I’ve checked the vm settings:
~$ timedatectl
Local time: Mi 2021-06-09 19:25:46 CEST
Universal time: Mi 2021-06-09 17:25:46 UTC
RTC time: Mi 2021-06-09 17:25:46
Time zone: Europe/Berlin (CEST, +0200)
System clock synchronized: yes
systemd-timesyncd.service active: yes
RTC in local TZ: no
Directly in XWiki we have Berlin as timezone too. Any suggestions?