Mysterious calendar entry shift?

Hi, i just encountered a very strange problem with my iPhone Calender. I have two Macs and an iPad. All showing an iCal calendar entry at 7.p.m Eastern Standard Time. Only my iPhone 5 shows the same appointment on Saturday 1am. I first thought that my iPhone/calender was set to the wrong timezone. But this is not the case, The phone is on New York time, the calender entry too. The icon on my phone says Friday 11, but when I open the calender the today button shows me Saturday the 12th (which would be true, if I would be in Europe). When I enter a new appintment it automatically shows Middle European timezone as standard, when I switch the appintment to Eastern Standard and save it. The appointment is shown at the European time zone (plus 6 hours). I tried it with automatic and manual timezone. Whatever I do, the iPhone calendar seems to be stuck with the European timezone. I already tried to close the app and to soft reset the iPhone, but no success. What have I missed?