diff --git a/polygerrit-ui/app/elements/shared/gr-date-formatter/gr-date-formatter.js b/polygerrit-ui/app/elements/shared/gr-date-formatter/gr-date-formatter.js
index c642936add..8e9653ce8c 100644
--- a/polygerrit-ui/app/elements/shared/gr-date-formatter/gr-date-formatter.js
+++ b/polygerrit-ui/app/elements/shared/gr-date-formatter/gr-date-formatter.js
@@ -37,11 +37,12 @@
       },
 
       _timeFormat: String,
+      _timeFormatPromise: Object, // Used for testing.
     },
 
     attached: function() {
-      this._getTimeFormat().then(function(timeFormat) {
-        this._timeFormat = timeFormat;
+      this._timeFormatPromise = this._getTimeFormat().then(function(tf) {
+        this._timeFormat = tf;
       }.bind(this));
     },
 
diff --git a/polygerrit-ui/app/elements/shared/gr-date-formatter/gr-date-formatter_test.html b/polygerrit-ui/app/elements/shared/gr-date-formatter/gr-date-formatter_test.html
index 341c7babfb..bdfd22b84d 100644
--- a/polygerrit-ui/app/elements/shared/gr-date-formatter/gr-date-formatter_test.html
+++ b/polygerrit-ui/app/elements/shared/gr-date-formatter/gr-date-formatter_test.html
@@ -129,14 +129,15 @@ limitations under the License.
     }
 
     suite('logged in', function() {
-      setup(function() {
+      setup(function(done) {
         return stubRestAPI(true, {time_format: 'HHMM_12'}).then(function() {
           element = fixture('basic');
+          done();
         });
       });
 
       test('Preferences are respected', function(done) {
-        flush(function() {
+        element._timeFormatPromise.then(function() {
           assert.equal(element._timeFormat, 'HHMM_12');
           done();
         });
@@ -144,14 +145,15 @@ limitations under the License.
     });
 
     suite('logged out', function() {
-      setup(function() {
+      setup(function(done) {
         return stubRestAPI(false, null).then(function() {
           element = fixture('basic');
+          done();
         });
       });
 
       test('Default preferences are respected', function(done) {
-        flush(function() {
+        element._timeFormatPromise.then(function() {
           assert.equal(element._timeFormat, 'HHMM_24');
           done();
         });