diff --git a/polygerrit-ui/app/utils/date-util_test.js b/polygerrit-ui/app/utils/date-util_test.js
deleted file mode 100644
index 96d5bc1..0000000
--- a/polygerrit-ui/app/utils/date-util_test.js
+++ /dev/null
@@ -1,144 +0,0 @@
-/**
- * @license
- * Copyright (C) 2020 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-import '../test/common-test-setup-karma.js';
-import {isValidDate, parseDate, fromNow, isWithinDay, isWithinHalfYear, formatDate, wasYesterday} from './date-util.js';
-
-suite('date-util tests', () => {
-  suite('parseDate', () => {
-    test('parseDate server date', () => {
-      const parsed = parseDate('2015-09-15 20:34:00.000000000');
-      assert.equal('2015-09-15T20:34:00.000Z', parsed.toISOString());
-    });
-  });
-
-  suite('isValidDate', () => {
-    test('date is valid', () => {
-      assert.isTrue(isValidDate(new Date()));
-    });
-    test('broken date is invalid', () => {
-      assert.isFalse(isValidDate(new Date('xxx')));
-    });
-  });
-
-  suite('fromNow', () => {
-    test('test all variants', () => {
-      const fakeNow = new Date('May 08 2020 12:00:00');
-      sinon.useFakeTimers(fakeNow.getTime());
-      assert.equal('just now', fromNow(new Date('May 08 2020 11:59:30')));
-      assert.equal('1 minute ago', fromNow(new Date('May 08 2020 11:59:00')));
-      assert.equal('5 minutes ago', fromNow(new Date('May 08 2020 11:55:00')));
-      assert.equal('1 hour ago', fromNow(new Date('May 08 2020 11:00:00')));
-      assert.equal(
-          '1 hour 5 min ago', fromNow(new Date('May 08 2020 10:55:00')));
-      assert.equal('3 hours ago', fromNow(new Date('May 08 2020 9:00:00')));
-      assert.equal('1 day ago', fromNow(new Date('May 07 2020 12:00:00')));
-      assert.equal('1 day 2 hr ago', fromNow(new Date('May 07 2020 10:00:00')));
-      assert.equal('3 days ago', fromNow(new Date('May 05 2020 12:00:00')));
-      assert.equal('1 month ago', fromNow(new Date('Apr 05 2020 12:00:00')));
-      assert.equal('2 months ago', fromNow(new Date('Mar 05 2020 12:00:00')));
-      assert.equal('1 year ago', fromNow(new Date('May 05 2019 12:00:00')));
-      assert.equal('10 years ago', fromNow(new Date('May 05 2010 12:00:00')));
-    });
-    test('rounding error', () => {
-      const fakeNow = new Date('May 08 2020 12:00:00');
-      sinon.useFakeTimers(fakeNow.getTime());
-      assert.equal('2 hours ago', fromNow(new Date('May 08 2020 9:30:00')));
-    });
-  });
-
-  suite('isWithinDay', () => {
-    test('basics works', () => {
-      assert.isTrue(isWithinDay(new Date('May 08 2020 12:00:00'),
-          new Date('May 08 2020 02:00:00')));
-      assert.isFalse(isWithinDay(new Date('May 08 2020 12:00:00'),
-          new Date('May 07 2020 12:00:00')));
-    });
-  });
-
-  suite('wasYesterday', () => {
-    test('less 24 hours', () => {
-      assert.isFalse(wasYesterday(new Date('May 08 2020 12:00:00'),
-          new Date('May 08 2020 02:00:00')));
-      assert.isTrue(wasYesterday(new Date('May 08 2020 12:00:00'),
-          new Date('May 07 2020 12:00:00')));
-    });
-    test('more 24 hours', () => {
-      assert.isTrue(wasYesterday(new Date('May 08 2020 12:00:00'),
-          new Date('May 07 2020 2:00:00')));
-      assert.isFalse(wasYesterday(new Date('May 08 2020 12:00:00'),
-          new Date('May 06 2020 14:00:00')));
-    });
-  });
-
-  suite('isWithinHalfYear', () => {
-    test('basics works', () => {
-      assert.isTrue(isWithinHalfYear(new Date('May 08 2020 12:00:00'),
-          new Date('Feb 08 2020 12:00:00')));
-      assert.isFalse(isWithinHalfYear(new Date('May 08 2020 12:00:00'),
-          new Date('Nov 07 2019 12:00:00')));
-    });
-  });
-
-  suite('formatDate', () => {
-    test('works for standard format', () => {
-      const stdFormat = 'MMM DD, YYYY';
-      assert.equal('May 08, 2020',
-          formatDate(new Date('May 08 2020 12:00:00'), stdFormat));
-      assert.equal('Feb 28, 2020',
-          formatDate(new Date('Feb 28 2020 12:00:00'), stdFormat));
-
-      const time24Format = 'HH:mm:ss';
-      assert.equal('Feb 28, 2020 12:01:12',
-          formatDate(new Date('Feb 28 2020 12:01:12'), stdFormat + ' '
-          + time24Format));
-    });
-    test('works for euro format', () => {
-      const euroFormat = 'DD.MM.YYYY';
-      assert.equal('01.12.2019',
-          formatDate(new Date('Dec 01 2019 12:00:00'), euroFormat));
-      assert.equal('20.01.2002',
-          formatDate(new Date('Jan 20 2002 12:00:00'), euroFormat));
-
-      const time24Format = 'HH:mm:ss';
-      assert.equal('28.02.2020 00:01:12',
-          formatDate(new Date('Feb 28 2020 00:01:12'), euroFormat + ' '
-          + time24Format));
-    });
-    test('works for iso format', () => {
-      const isoFormat = 'YYYY-MM-DD';
-      assert.equal('2015-01-01',
-          formatDate(new Date('Jan 01 2015 12:00:00'), isoFormat));
-      assert.equal('2013-07-03',
-          formatDate(new Date('Jul 03 2013 12:00:00'), isoFormat));
-
-      const timeFormat = 'h:mm:ss A';
-      assert.equal('2013-07-03 5:00:00 AM',
-          formatDate(new Date('Jul 03 2013 05:00:00'), isoFormat + ' '
-          + timeFormat));
-      assert.equal('2013-07-03 5:00:00 PM',
-          formatDate(new Date('Jul 03 2013 17:00:00'), isoFormat + ' '
-          + timeFormat));
-    });
-    test('h:mm:ss A shows correctly midnight and midday', () => {
-      const timeFormat = 'h:mm A';
-      assert.equal('12:14 PM',
-          formatDate(new Date('Jul 03 2013 12:14:00'), timeFormat));
-      assert.equal('12:15 AM',
-          formatDate(new Date('Jul 03 2013 00:15:00'), timeFormat));
-    });
-  });
-});
diff --git a/polygerrit-ui/app/utils/date-util_test.ts b/polygerrit-ui/app/utils/date-util_test.ts
new file mode 100644
index 0000000..f17ced3
--- /dev/null
+++ b/polygerrit-ui/app/utils/date-util_test.ts
@@ -0,0 +1,219 @@
+/**
+ * @license
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import {Timestamp} from '../types/common';
+import '../test/common-test-setup-karma';
+import {
+  isValidDate,
+  parseDate,
+  fromNow,
+  isWithinDay,
+  isWithinHalfYear,
+  formatDate,
+  wasYesterday,
+} from './date-util';
+
+suite('date-util tests', () => {
+  suite('parseDate', () => {
+    test('parseDate server date', () => {
+      const parsed = parseDate('2015-09-15 20:34:00.000000000' as Timestamp);
+      assert.equal('2015-09-15T20:34:00.000Z', parsed.toISOString());
+    });
+  });
+
+  suite('isValidDate', () => {
+    test('date is valid', () => {
+      assert.isTrue(isValidDate(new Date()));
+    });
+    test('broken date is invalid', () => {
+      assert.isFalse(isValidDate(new Date('xxx')));
+    });
+  });
+
+  suite('fromNow', () => {
+    test('test all variants', () => {
+      const fakeNow = new Date('May 08 2020 12:00:00');
+      sinon.useFakeTimers(fakeNow.getTime());
+      assert.equal('just now', fromNow(new Date('May 08 2020 11:59:30')));
+      assert.equal('1 minute ago', fromNow(new Date('May 08 2020 11:59:00')));
+      assert.equal('5 minutes ago', fromNow(new Date('May 08 2020 11:55:00')));
+      assert.equal('1 hour ago', fromNow(new Date('May 08 2020 11:00:00')));
+      assert.equal(
+        '1 hour 5 min ago',
+        fromNow(new Date('May 08 2020 10:55:00'))
+      );
+      assert.equal('3 hours ago', fromNow(new Date('May 08 2020 9:00:00')));
+      assert.equal('1 day ago', fromNow(new Date('May 07 2020 12:00:00')));
+      assert.equal('1 day 2 hr ago', fromNow(new Date('May 07 2020 10:00:00')));
+      assert.equal('3 days ago', fromNow(new Date('May 05 2020 12:00:00')));
+      assert.equal('1 month ago', fromNow(new Date('Apr 05 2020 12:00:00')));
+      assert.equal('2 months ago', fromNow(new Date('Mar 05 2020 12:00:00')));
+      assert.equal('1 year ago', fromNow(new Date('May 05 2019 12:00:00')));
+      assert.equal('10 years ago', fromNow(new Date('May 05 2010 12:00:00')));
+    });
+    test('rounding error', () => {
+      const fakeNow = new Date('May 08 2020 12:00:00');
+      sinon.useFakeTimers(fakeNow.getTime());
+      assert.equal('2 hours ago', fromNow(new Date('May 08 2020 9:30:00')));
+    });
+  });
+
+  suite('isWithinDay', () => {
+    test('basics works', () => {
+      assert.isTrue(
+        isWithinDay(
+          new Date('May 08 2020 12:00:00'),
+          new Date('May 08 2020 02:00:00')
+        )
+      );
+      assert.isFalse(
+        isWithinDay(
+          new Date('May 08 2020 12:00:00'),
+          new Date('May 07 2020 12:00:00')
+        )
+      );
+    });
+  });
+
+  suite('wasYesterday', () => {
+    test('less 24 hours', () => {
+      assert.isFalse(
+        wasYesterday(
+          new Date('May 08 2020 12:00:00'),
+          new Date('May 08 2020 02:00:00')
+        )
+      );
+      assert.isTrue(
+        wasYesterday(
+          new Date('May 08 2020 12:00:00'),
+          new Date('May 07 2020 12:00:00')
+        )
+      );
+    });
+    test('more 24 hours', () => {
+      assert.isTrue(
+        wasYesterday(
+          new Date('May 08 2020 12:00:00'),
+          new Date('May 07 2020 2:00:00')
+        )
+      );
+      assert.isFalse(
+        wasYesterday(
+          new Date('May 08 2020 12:00:00'),
+          new Date('May 06 2020 14:00:00')
+        )
+      );
+    });
+  });
+
+  suite('isWithinHalfYear', () => {
+    test('basics works', () => {
+      assert.isTrue(
+        isWithinHalfYear(
+          new Date('May 08 2020 12:00:00'),
+          new Date('Feb 08 2020 12:00:00')
+        )
+      );
+      assert.isFalse(
+        isWithinHalfYear(
+          new Date('May 08 2020 12:00:00'),
+          new Date('Nov 07 2019 12:00:00')
+        )
+      );
+    });
+  });
+
+  suite('formatDate', () => {
+    test('works for standard format', () => {
+      const stdFormat = 'MMM DD, YYYY';
+      assert.equal(
+        'May 08, 2020',
+        formatDate(new Date('May 08 2020 12:00:00'), stdFormat)
+      );
+      assert.equal(
+        'Feb 28, 2020',
+        formatDate(new Date('Feb 28 2020 12:00:00'), stdFormat)
+      );
+
+      const time24Format = 'HH:mm:ss';
+      assert.equal(
+        'Feb 28, 2020 12:01:12',
+        formatDate(
+          new Date('Feb 28 2020 12:01:12'),
+          stdFormat + ' ' + time24Format
+        )
+      );
+    });
+    test('works for euro format', () => {
+      const euroFormat = 'DD.MM.YYYY';
+      assert.equal(
+        '01.12.2019',
+        formatDate(new Date('Dec 01 2019 12:00:00'), euroFormat)
+      );
+      assert.equal(
+        '20.01.2002',
+        formatDate(new Date('Jan 20 2002 12:00:00'), euroFormat)
+      );
+
+      const time24Format = 'HH:mm:ss';
+      assert.equal(
+        '28.02.2020 00:01:12',
+        formatDate(
+          new Date('Feb 28 2020 00:01:12'),
+          euroFormat + ' ' + time24Format
+        )
+      );
+    });
+    test('works for iso format', () => {
+      const isoFormat = 'YYYY-MM-DD';
+      assert.equal(
+        '2015-01-01',
+        formatDate(new Date('Jan 01 2015 12:00:00'), isoFormat)
+      );
+      assert.equal(
+        '2013-07-03',
+        formatDate(new Date('Jul 03 2013 12:00:00'), isoFormat)
+      );
+
+      const timeFormat = 'h:mm:ss A';
+      assert.equal(
+        '2013-07-03 5:00:00 AM',
+        formatDate(
+          new Date('Jul 03 2013 05:00:00'),
+          isoFormat + ' ' + timeFormat
+        )
+      );
+      assert.equal(
+        '2013-07-03 5:00:00 PM',
+        formatDate(
+          new Date('Jul 03 2013 17:00:00'),
+          isoFormat + ' ' + timeFormat
+        )
+      );
+    });
+    test('h:mm:ss A shows correctly midnight and midday', () => {
+      const timeFormat = 'h:mm A';
+      assert.equal(
+        '12:14 PM',
+        formatDate(new Date('Jul 03 2013 12:14:00'), timeFormat)
+      );
+      assert.equal(
+        '12:15 AM',
+        formatDate(new Date('Jul 03 2013 00:15:00'), timeFormat)
+      );
+    });
+  });
+});