Use gr-date-formatter to display checker start time

Change-Id: I2ec03e44e230786857cf3d97e15c5e0b049d9511
diff --git a/gr-checks/gr-checks-item.html b/gr-checks/gr-checks-item.html
index 374f76b..fb9c669 100644
--- a/gr-checks/gr-checks-item.html
+++ b/gr-checks/gr-checks-item.html
@@ -35,7 +35,13 @@
       <gr-checks-status show-text status="[[check.state]]" downgrade-failure-to-warning="[[false]]"></gr-checks-status>
     </td>
     <td><!--Check System--></td>
-    <td>[[_startTime]]</td>
+    <td>
+      <gr-date-formatter
+        has-tooltip
+        show-date-and-time
+        date-str="[[_startTime]]">
+      </gr-date-formatter>
+    </td>
     <td>[[_duration]]</td>
     <td>
       <a href$="[[check.url]]" target="_blank" class="log">
diff --git a/gr-checks/gr-checks-item.js b/gr-checks/gr-checks-item.js
index 44198bc..572ba2e 100644
--- a/gr-checks/gr-checks-item.js
+++ b/gr-checks/gr-checks-item.js
@@ -59,7 +59,7 @@
      */
     _computeStartTime(check) {
       if (!check.started) return "-";
-      return moment(check.started).format('LTS');
+      return check.started;
     },
 
     _toggleMessageShown() {