I put in 10:00 for end date but upon reopening, it says 11:00. I can confirm that the wrong date is sent to the server as well as I got complaints about it this week.
This only happen when I create an event spanning the DST.
The fix was merged to our repo, it will be available in the tomorrow nightly or in the 5.5.3 release. To activate the fix, you will need to enable the adjustDurationToDST option in the project like this:
new Scheduler({
project : { adjustDurationToDST : true }
})