DatatypeNormalizer/DateTimeNormalizer.php
public function supportsNormalization($data, $format = null)
    {
        return is_object($data) && ($data instanceof \DateTime) && (self::FORMAT === $format);
    }
public function supportsNormalization($data, $format = null)
    {
        return is_object($data) && ($data instanceof \DateTime) && (self::FORMAT === $format);
    }
Checks whether the given class is supported for normalization by this normalizer

@param mixed  $data   Data to normalize.
@param string $format The format being (de-)serialized from or into.

@return Boolean