code: public static function getInputFormat($strFormat=null)
  	{
  		if ($strFormat === null)
  		{
  			$strFormat = static::getNumericDateFormat();
  		}
  
  		if (!static::isNumericFormat($strFormat))
  		{
  			throw new \Exception(sprintf('Invalid date format "%s"', $strFormat));
  		}
  
  		$arrCharacterMapper = array();
  
  		foreach ($GLOBALS['TL_LANG']['DATE'] as $k=>$v)
  		{
  			$arrCharacterMapper[$k] = $v;
  		}
  
  		$arrInputFormat = array();
  		$arrCharacters = str_split($strFormat);
  
  		foreach ($arrCharacters as $strCharacter)
  		{
  			if (isset($arrCharacterMapper[$strCharacter]))
  			{
  				$arrInputFormat[$strFormat] .= $arrCharacterMapper[$strCharacter];
  			}
  			else
  			{
  				$arrInputFormat[$strFormat] .= $strCharacter;
  			}
  		}
  
  		return $arrInputFormat[$strFormat];
  	}
docs: Return an input format string for a particular date (e.g. YYYY-MM-DD)
  
  @param string $strFormat An optional format string
  
  @return string The input format string
  
  @throws \Exception If $strFormat is invalid