A graphical user interface system for a thermal comfort controller. The user interface system has a central processing unit coupled to a memory and a touch sensitive display unit. The memory stores a temperature schedule data structure and perhaps a temperature history data structure. The temperature schedule data structure is made up of at least one set-point. The temperature history data structure is made up of at least one Actual-Temperature-Point. The display presents the set-points and/or the Actual-Temperature-Points. One representation of the display is a graphical step-function. The user uses a finger or stylus to program the set-points by pointing and dragging a portion of the step-function.