Graph to represent an average time

I need some statistics to show when a motor is turning on and off.
Imagine a graph, a visual representation showing when that motor is coming on with a second  less important element showing when it went off.

Over a period of time, I should be able to SEE averages showing when that motor was coming on. Lets say we are looking at a month of logging, we should now be able to see that the motor constantly came on mid afternoon last week, randomly the week before but before that, it mostly always came on early afternoons.

I need to show the viewer that average when the motor is coming on over the course of a week, month, months, year, etc.

Prefer to use nvd3 since it's something we are already using.

Attached are examples which are not really working well for many reasons. In one, the viewer thinks the filled in lower area of the bar is representing that the start time was 00:00am to Y axis. Need a better way to represent this. The top of each bar represents the start time. Or, is supposed to but is confusing to the user at the moment.

In the second two examples, one is showing a short period of time while the other is showing 60 days.
Making the bottoms white to try and show the start/end times isn't working well either.

Can't seem to find the right way of representing this data using an NVD3 graph.
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