diff --git a/src/Composer/Package/Dumper/ArrayDumper.php b/src/Composer/Package/Dumper/ArrayDumper.php
index 714c5183b..faea5666a 100644
--- a/src/Composer/Package/Dumper/ArrayDumper.php
+++ b/src/Composer/Package/Dumper/ArrayDumper.php
@@ -83,7 +83,7 @@ class ArrayDumper
         }
 
         if ($package->getReleaseDate()) {
-            $data['time'] = $package->getReleaseDate()->format('Y-m-d H:i:s');
+            $data['time'] = $package->getReleaseDate()->format(DATE_RFC3339);
         }
 
         $data = $this->dumpValues($package, $keys, $data);
diff --git a/tests/Composer/Test/Package/Dumper/ArrayDumperTest.php b/tests/Composer/Test/Package/Dumper/ArrayDumperTest.php
index c2c820fb1..bf4eef6b7 100644
--- a/tests/Composer/Test/Package/Dumper/ArrayDumperTest.php
+++ b/tests/Composer/Test/Package/Dumper/ArrayDumperTest.php
@@ -104,9 +104,9 @@ class ArrayDumperTest extends \PHPUnit_Framework_TestCase
             ),
             array(
                 'time',
-                new \DateTime('2012-02-01'),
+                $datetime = new \DateTime('2012-02-01'),
                 'ReleaseDate',
-                '2012-02-01 00:00:00',
+                $datetime->format(DATE_RFC3339),
             ),
             array(
                 'authors',