I have built a PHP calendar system and have pretty much everything done but not sure how to deal with a UI issue involving how the events that stretched out over a couple of days. I want to be able to stretch an event that stretches over couple of days in a div that spans those days in the calendar. Basically I would like to know how to achieve what these guys have achieved with the event that stretches out from 21st to 22nd with the yellow div background.

I have been trying to see how I can do it with PHP but I feel like I might be trying the wrong thing. Perhaps this is done with javascript?