AuctionController.php

/**
	 * Property Mapping Setup
	 *
	 * @return void
	 */
	public function initializeCreateOverlayAction() {

		$propertyMappingConfiguration = $this->arguments['since']->getPropertyMappingConfiguration();
		$propertyMappingConfiguration->setTypeConverterOption('TYPO3\\CMS\\Extbase\\Property\\TypeConverter\\DateTimeConverter', \TYPO3\CMS\Extbase\Property\TypeConverter\DateTimeConverter::CONFIGURATION_DATE_FORMAT, 'Y-m-d');

		// PropertyMappingConfiguration for Resource
		$resourcePropertyMappingConfiguration = $this->arguments[$this->resourceArgumentName]->getPropertyMappingConfiguration();
		$resourcePropertyMappingConfiguration->setTypeConverterOption('TYPO3\CMS\Extbase\Property\TypeConverter\PersistentObjectConverter', \TYPO3\CMS\Extbase\Property\TypeConverter\PersistentObjectConverter::CONFIGURATION_MODIFICATION_ALLOWED, true);
		$resourcePropertyMappingConfiguration->allowAllPropertiesExcept('number');
	}