I think you have to add custom validation function. This is how I did it.
// In rules
array('start_time', 'validateTime')
// Add below functions to your model
public function validateTime()
{
if (!$this->compareTime($this->start_time, $this->end_time))
{
$this->addError('start_time', 'Start time should less than End time');
}
}
public function compareTime($start, $end)
{
list($start_hr, $start_min) = str_split(preg_replace('/[:]/', '', $start), 2);
list($end_hr, $end_min) = str_split(preg_replace('/[:]/', '', $end), 2);
return ($start_hr *60 + $start_min) < ($end_hr * 60 + $end_min);
}
Assume your time input is in hh:mm format.I used CJuiDateTimePicker to select time.