src/User/Service/User.php
public function dateToSqlFormat($dateString) 
	{		
    	$dateFormatter = new \IntlDateFormatter(
			\Locale::getDefault(),
			\IntlDateFormatter::NONE,
			\IntlDateFormatter::NONE,
			\date_default_timezone_get(),
			\IntlDateFormatter::GREGORIAN,
			"dd MMM yyyy"
    	);
    	$time = $dateFormatter->parse($dateString);
    	$date = new \DateTime();
    	$date->setTimestamp($time);
    	
    	return $date->format('Y-m-d');
   }
public function dateToSqlFormat($dateString) 
	{		
    	$dateFormatter = new \IntlDateFormatter(
			\Locale::getDefault(),
			\IntlDateFormatter::NONE,
			\IntlDateFormatter::NONE,
			\date_default_timezone_get(),
			\IntlDateFormatter::GREGORIAN,
			"dd MMM yyyy"
    	);
    	$time = $dateFormatter->parse($dateString);
    	$date = new \DateTime();
    	$date->setTimestamp($time);
    	
    	return $date->format('Y-m-d');
   }
Format from "dd MMM yyyy" to "Y-m-d"

@param string $dateString
@return string