Secondary X axis labels for History dashboard

[HenryLoenwind]

It would be very nice if the graph(s) in the History Dashboard had secondary labels on the X axis in "relative time to now".

I regularly look at something in the history and ask myself, "How long ago was that?" I can do the math using the absolute time (and date) shown, but it is cumbersome.

Mockup:

PS: Same for the time/date display in the mouseover popup.