Tasks appearing in wrong time in calendar module

I am afraid I donā€™t knowā€¦

I know that due_date vs start_date is a particularly tricky issue with SuiteCRM, because of the aggregating subpanel called ā€œactivitiesā€, which uses dates from several modules and tries to make sense of them. There have been several bugs and regressions with these fields in that subpanel.

But I am not sure what is supposed to be going on in the calendar.

This thread has some info about the fullCalendar options to make things draggable: