First step. You can make your own validation rules in your model.
public function rules()
{
array('timefield', 'validateTimeField'),
}
// Custom validation for time field.
public function validateTimeField($attribute,$params)
{
if(do some checks here...)
{
$this->addError($attribute, $this->getAttributeLabel('Error because bla bla.');
}
if(do some more checks here...)
{
$this->addError($attribute, $this->getAttributeLabel('Error because...');
}
}