Portlets - changes timezone automatically (plone 6 classic ui)

I’m working with Plone 6.1.0 and I’m using event Portlets in den UI on the right hand side. It shows me the newst 2 events. With the title, date and time and description. I noticed that the date and time change randomly in the american timezone.

I checked the date and time in den plone konfiguration - I set it so Europe/Vienna, and also the timezone for each user.

Does anyone else have this problem? Or any ideas on how I can solve this so that the website doesn't constantly change the time zone?

Thank you very much! BR Marlene