Clock not working properly

1. A concise explanation of the problem you're experiencing.

The timeline at the bottom seems not to work with the provided start time and stop time.

Regardless of what value I set; it is always set based on the todays day.

2. A minimal code example. If you've found a bug, this helps us reproduce and repair it.

        viewer.clock.startTime = sampledPositions.startTime.clone();
        viewer.clock.stopTime = sampledPositions.endTime.clone();
        viewer.clock.currentTime = sampledPositions.startTime.clone();
        viewer.clock.clockRange = Cesium.ClockRange.LOOP_STOP;

viewer.clock.startTime.toString()
"2017-09-08T03:31:46Z"

viewer.clock.stopTime.toString()
"2017-09-08T23:59:58Z"

However, the time line on the bottom shows March 14 2018.

3. Context. Why do you need to do this? We might know a better way to accomplish your goal.

Visualize certain date period.

4. The Cesium version you're using, your operating system and browser.
"cesium": "^1.42.1",

Resolved. I was forgetting to do viewer.timeline.zoomTo

Thanks for updating with your solution!