Revo 2.5 - Problem with events longer than 30 days

[mediengaarage]

I use mxCalendar 1.1.11 in ModX 2.5.4 an it works great.
Only when i have an event its longer than 30 days, then it show as end date the next month not the month after.
I have an event from 29.07. to 11.09. and the end date it is shown is 11.08.
In the backend of mxCalendar is the right end date.