diff --git a/src/GraphNode/GraphNode.php b/src/GraphNode/GraphNode.php
index 8f4ff35dd..e89553af5 100644
--- a/src/GraphNode/GraphNode.php
+++ b/src/GraphNode/GraphNode.php
@@ -275,28 +275,6 @@ public function isIso8601DateString($string)
         return preg_match($crazyInsaneRegexThatSomehowDetectsIso8601, $string) === 1;
     }
 
-    /**
-     * Determines if a value from Graph should be cast to DateTime.
-     *
-     * @param string $key
-     *
-     * @return bool
-     */
-    public function shouldCastAsDateTime($key)
-    {
-        return in_array($key, [
-            'created_time',
-            'updated_time',
-            'start_time',
-            'stop_time',
-            'end_time',
-            'backdated_time',
-            'issued_at',
-            'expires_at',
-            'publish_time'
-        ], true);
-    }
-
     /**
      * Casts a date value from Graph to DateTime.
      *
@@ -337,4 +315,26 @@ public static function getNodeMap()
     {
         return static::$graphNodeMap;
     }
+
+    /**
+     * Determines if a value from Graph should be cast to DateTime.
+     *
+     * @param string $key
+     *
+     * @return bool
+     */
+    private function shouldCastAsDateTime($key)
+    {
+        return in_array($key, [
+            'created_time',
+            'updated_time',
+            'start_time',
+            'stop_time',
+            'end_time',
+            'backdated_time',
+            'issued_at',
+            'expires_at',
+            'publish_time'
+        ], true);
+    }
 }
diff --git a/tests/GraphNode/GraphNodeTest.php b/tests/GraphNode/GraphNodeTest.php
index 84f8c8c9d..713179844 100644
--- a/tests/GraphNode/GraphNodeTest.php
+++ b/tests/GraphNode/GraphNodeTest.php
@@ -43,6 +43,29 @@ public function testAGraphNodeCanInstantiateWithData()
         $this->assertEquals(['foo' => 'bar'], $backingData);
     }
 
+    /**
+     * @dataProvider provideDateTimeFieldNames
+     */
+    public function testIsCastDateTimeFieldsToDateTime($fieldName)
+    {
+        $graphNode = new GraphNode([$fieldName => '1989-11-02']);
+
+        $this->assertInstanceOf(\DateTime::class, $graphNode->getField($fieldName));
+    }
+
+    public static function provideDateTimeFieldNames()
+    {
+        yield ['created_time'];
+        yield ['updated_time'];
+        yield ['start_time'];
+        yield ['stop_time'];
+        yield ['end_time'];
+        yield ['backdated_time'];
+        yield ['issued_at'];
+        yield ['expires_at'];
+        yield ['publish_time'];
+    }
+
     public function testDatesThatShouldBeCastAsDateTimeObjectsAreDetected()
     {
         $graphNode = new GraphNode();