1. Go to calendar.google.com
2. Create some event by clicking on the calendar
The event is created at wrong time and manually adjusting time by "Edit event" doesn't work either. It appears that the script on the page is totally confused.
I cannot reproduce after doing the fix for: https://bugs.webkit.org/show_bug.cgi?id=66010
*** This bug has been marked as a duplicate of bug 66010 ***