DateTimeConverter

public function initializeCreateAction()
{
	$this->setDateTimePropertyDateTimeConverter('newModel','dateStart');
}    
public function initializeUpdateAction()
{
	$this->setDateTimePropertyDateTimeConverter('model','dateStart');
}
protected function setDateTimePropertyDateTimeConverter($modelName,$propertyName){
	$this->arguments[$modelName]
	->getPropertyMappingConfiguration()
	->forProperty($propertyName)
	->setTypeConverterOption('TYPO3\CMS\Extbase\Property\TypeConverter\DateTimeConverter', 
	\TYPO3\CMS\Extbase\Property\TypeConverter\DateTimeConverter::CONFIGURATION_DATE_FORMAT, 
	'd-m-y');		
}