Add option to compare multiple days in one graph

[michaelschwarz]

I didn't find any option, so assuming this doesn't exit.

The feature request is to compare multiple days in a diagram graph, i.e. the last week but overlaying each to compare same period.

Example: solar energy by day over a week
The x-axis shows 00:00-24:00, older days line is shown more transparent, so up to earliest time period is fully drawn.