Incorrect event overlap


I’m evaluating DHTMLX scheduler pro with a sample code downloaded from “Hotel Room Reservation Calendar
in HTML5/JavaScript and PHP/MySQL”

When I customized the code to allow event overlap, a strange thing happened. The two event overlapped.
Please see the screen shot.

the events conditions are
check-in:08/19 check-out:08/21
check-in:08/21 check-out:08/22

I think two events doesn’t overlap with this condition.
In this case, I think that it will be displayed in one line.

Couuld I have any help or suggestion, please?

please check start/end_date values of these events, overlapping must be caused by date values.
You can find ids of these events using DOM inspector
and then inspect event objects in browser console: scheduler.getEvent(eventId);