The RadTimePicker control uses skins to control the overall look-and-feel of the control. A skin is a set of images and a CSS stylesheet that can be applied to the control elements (date cells, buttons, etc.) and defines their look and feel. To apply a skin to a RadTimePicker control, set its Skin property, either using the properties pane or the control's Smart Tag.
On RadTimePicker the Skin property value is always propagated to the child controls (the embedded RadDateInput and popup RadTimeView controls).
If you do not set the Skin property, the RadTimePicker will automatically use the "Default" skin. If you do not want to use a skin with your control, set its Skin property to an empty string. If you also want to prevent the control's base stylesheet from registering, please set EnableEmbeddedBaseStylesheet to false. The base stylesheet contains CSS styles, which are applied to the RadTimePicker control instances, regardless of their skin name, because these styles are the same for all skins. These base styles include alignment, positioning, border widths, paddings, etc.
For more information on how you can customize the skins, please refer to the RadCalendar Skins article.