Refactoring some Unit Test that have lots of repeated code.

I am working on writing some some tests for a function I wrote: the current code works as I would expect it but now I need to DRY my code and refactor. Below you will see the unit tests I've writtern:

QUnit.test('Localized Date in Honolulu', assert => {
  const stub = sinon.stub(constantDate, 'getTimezoneOffset', () => {
    return '600';
  });
  console.log('timeSet', timeSet());
  assert.strictEqual(timeSet(), '2017-07-29T14:00:00.000Z', 'there needs to be a message here');
  stub.restore();
});

QUnit.test('San Francisco Date and Time', assert => {
  const stub = sinon.stub(constantDate, 'getTimezoneOffset', () => {
    return '420';
  });
  assert.strictEqual(timeSet(), '2017-07-29T17:00:00.000Z');
  stub.restore();
});

QUnit.test('Sydney time', assert => {
  const stub = sinon.stub(constantDate, 'getTimezoneOffset', () => {
    return '-600';
  });
  assert.strictEqual(timeSet(), '2017-07-30T10:00:00.000Z', 'Expected the time in Sydney to be 10AM');
  stub.restore();
});

Although it seems to me that I should be able to refactor the stub I'm finding challenging because every stub has a different return value every time. Can I please get some suggestions as to how I can make my code clean and DRY.