I cannot offer much details on my Problem yet, As i do not know where to start. I am not a Programmer.
Over Night I ran into a problem with my shop. All generated PDF files show a wrong date format. Like 08.03.2016 That's how it is also displayed in the html source code of my site (its UTF-8!) but the browser shows it right. My Dates come from a timestamp in MySQL and are formatted like this: {$event_date|date_format:"%e. %B %Y"} PDFs are created with (http://www.tcpdf.org) (TCPDF)
Now I have no clue where to start my search. Any Ideas? (I am on a managed server, I didn't do any changes to the system so may be the server environment changed. What could cause such a behavior?)