fix timezone problem

src/Serializer/Handler/CarbonHandler.php

@@ -70,6 +70,9 @@ class CarbonHandler implements SubscribingHandlerInterface
      */
     public function serializeCarbon(VisitorInterface $visitor, Carbon $date, array $type, Context $context)
     {
+        $date = clone $date;
+        $date->setTimezone($this->defaultTimezone);
+
         return $visitor->visitString($date->format($this->getFormat($type)), $type, $context);
     }
 
@@ -94,6 +97,8 @@ class CarbonHandler implements SubscribingHandlerInterface
             throw new RuntimeException(sprintf('Invalid datetime "%s", expected format %s.', $data, $format));
         }
 
+        $datetime->setTimezone(new \DateTimeZone(date_default_timezone_get()));
+
         return $datetime;
     }