Thank you! Yes it is a theme issue. We are programming it ourselves and a php include function is messing with the time. We don′t know why but thank you, now we at least know what the problem is!!
Sadly, it is not a plugin conflict. We disabled everything we installed recently and every puglin possible to disable. The time in the sidebar stayed wrong.
Sorry, I think I discribed it wrong. We don′t want to see the event details page (this is what we have set right know), we want see a diffrent page from the website if you click on the event in the grid calendar. It that possible?