Unfortunately the DateTimePicker control which the Calendar form control uses do not support disabling seconds only. I'm not sure about your requirements & usage, but if this is really important for you (important because you can always ignore seconds in your logic) you can always create your own form control using 3rd party calendar which might support it (google jQuery/bootstrap calendar - eg: http://www.learningjquery.com/2015/03/14-top-calendar-and-date-picker-jquery-plugins)