diff --git a/endpoints/api/repository.py b/endpoints/api/repository.py
index 84d07bec3..74f494112 100644
--- a/endpoints/api/repository.py
+++ b/endpoints/api/repository.py
@@ -177,13 +177,17 @@ class Repository(RepositoryParamResource):
     logger.debug('Get repo: %s/%s' % (namespace, repository))
 
     def tag_view(tag):
-      return {
+      tag_info = {
         'name': tag.name,
         'image_id': tag.image.docker_image_id,
-        'last_modified': format_date(datetime.datetime.fromtimestamp(tag.lifetime_start_ts)),
         'size': tag.image.storage.aggregate_size
       }
 
+      if tag.lifetime_start_ts > 0:
+        tag_info['last_modified'] = format_date(datetime.datetime.fromtimestamp(tag.lifetime_start_ts))
+
+      return tag_info
+
     organization = None
     try:
       organization = model.get_organization(namespace)
diff --git a/static/directives/repo-view/repo-panel-tags.html b/static/directives/repo-view/repo-panel-tags.html
index 4b25bd515..be238cf1c 100644
--- a/static/directives/repo-view/repo-panel-tags.html
+++ b/static/directives/repo-view/repo-panel-tags.html
@@ -60,7 +60,10 @@
          ng-class="checkedTags.isChecked(tag, checkedTags.checked) ? 'checked' : ''">
       <td><span class="cor-checkable-item" controller="checkedTags" item="tag"></span></td>
       <td><i class="fa fa-tag"></i> {{ tag.name }}</td>
-      <td><span am-time-ago="tag.last_modified"></span></td>
+      <td>
+        <span am-time-ago="tag.last_modified" ng-if="tag.last_modified"></span>
+        <span ng-if="!tag.last_modified">Unknown</span>
+      </td>
       <td>{{ tag.size | bytes }}</td>
       <td class="image-id-col">
         <a ng-href="/repository/{{ repository.namespace }}/{{ repository.name }}/image/{{ tag.image_id }}">
diff --git a/static/js/directives/repo-view/repo-panel-tags.js b/static/js/directives/repo-view/repo-panel-tags.js
index 6d845796e..add0db228 100644
--- a/static/js/directives/repo-view/repo-panel-tags.js
+++ b/static/js/directives/repo-view/repo-panel-tags.js
@@ -46,9 +46,10 @@ angular.module('quay').directive('repoPanelTags', function () {
         for (var tag in $scope.repository.tags) {
           if (!$scope.repository.tags.hasOwnProperty(tag)) { continue; }
 
-          var tagInfo = $.extend($scope.repository.tags[tag], {
+          var tagData = $scope.repository.tags[tag];
+          var tagInfo = $.extend(tagData, {
             'name': tag,
-            'last_modified_datetime': new Date($scope.repository.tags[tag].last_modified)
+            'last_modified_datetime': (new Date(tagData.last_modified || 0)).valueOf() * (-1)
           });
 
           allTags.push(tagInfo);