Event time is wrong and cannot be changed

When I create an event at 18:00, the time is automatically set to 18:06 where 06 seems to be the current minute. So, all events have an arbitrary minute at the end and not the minute I want them to start. 

When I want to change this afterwards, the time changes in the form only but not in the event itself. So, I cant change the time of events. The form shows the correct (changed) time. 

