diff --git a/app/Models/MetricPoint.php b/app/Models/MetricPoint.php
index f06832e8..88901f16 100644
--- a/app/Models/MetricPoint.php
+++ b/app/Models/MetricPoint.php
@@ -92,13 +92,17 @@ class MetricPoint extends Model implements HasPresenter
     /**
      * Round the created at value into intervals of 30 seconds.
      *
-     * @param string $value
+     * @param string $createdAt
      *
-     * @return void
+     * @return string|void
      */
-    public function setCreatedAtAttribute($value)
+    public function setCreatedAtAttribute($createdAt)
     {
-        $timestamp = $value->format('U');
+        if (!$createdAt) return;
+
+        $createdAt = Carbon::parse($createdAt);
+
+        $timestamp = $createdAt->format('U');
         $timestamp = 30 * round($timestamp / 30);
 
         return Carbon::createFromFormat('U', $timestamp)->toDateTimeString();
diff --git a/tests/Api/MetricPointTest.php b/tests/Api/MetricPointTest.php
index b11d3cc1..a603c9ae 100644
--- a/tests/Api/MetricPointTest.php
+++ b/tests/Api/MetricPointTest.php
@@ -78,11 +78,12 @@ class MetricPointTest extends AbstractApiTestCase
         $postData['timestamp'] = $timestamp;
 
         $response = $this->json('POST', "/api/v1/metrics/{$metric->id}/points", $postData);
+        $response->dump();
 
         $response->assertStatus(200);
         $response->assertJsonFragment([
             'value'      => $metricPoint->value,
-            'created_at' => date('Y-m-d H:i:s', 1434369116),
+            'created_at' => date('Y-m-d H:i:00', 1434369116),
         ]);
     }