Shade a portion of the graph by times on x-axis

[jevburchell]

Hi folks,

Is there a way to shade part of a graph's background?

Use case: I have a graph spanning 24 hours with battery state of charge (%) on the Y-axis and time (hours) on the X-axis. I have an offpeak cheap energy period between 00:30 and 04:30 each day, and I'd like this area of the chart to appear as shaded/highlighted to make it obvious where my offpeak battery charging fits. See here for the graph in question:

If anyone knows how to code this I'd be most grateful.

Cheers,
Jev