Merge pull request #1561 from thomasphansen/th_jsonformatter_use_formatdate

JsonFormatter::normalize() : respect date format from Formatter

src/Monolog/Formatter/JsonFormatter.php

@@ -44,6 +44,8 @@ class JsonFormatter extends NormalizerFormatter
         $this->batchMode = $batchMode;
         $this->appendNewline = $appendNewline;
         $this->ignoreEmptyContextAndExtra = $ignoreEmptyContextAndExtra;
+
+        parent::__construct();
     }
 
     /**
@@ -173,6 +175,10 @@ class JsonFormatter extends NormalizerFormatter
             return $normalized;
         }
 
+        if ($data instanceof \DateTimeInterface) {
+            return $this->formatDate($data);
+        }
+
         if ($data instanceof Throwable) {
             return $this->normalizeException($data, $depth);
         }