I think you've replicated the problem perfectly!
When running the script as you've created it, I get a blank chart (as per the first screenshot). When I change the line Date: new Date(1970, 0, 1 + i) to Date: new Date(1970, 0, 2 + i) (i.e. changing it from starting on 1/1/1970 to starting on 2/1/1970) the chart displays as per my second screenshot.
I've tried this in Chrome 50.0.2661, Firefox 45.0.2 and IE11 and I see the same behaviour everywhere.