Would "temporal proximity" be an effective way to label the axis of a graph?

I have a bunch of events that vary in duration and also vary in how recently they occurred. I want to graph these events so that they look like a typical bar graph, with all the bases resting on the X axis and the Y axis representing time. This way it will be easy to see which events lasted longer than other events (the taller the bar, the longer the duration of the event). But I also want to express how far in the past each event took place. More recent events would be closer to the origin than the ones further back in history.

I think "duration" is a good label for the Y axis, with "hours" being the unit of measure. As for the X axis, I'm having a harder time deciding on a way to describe the property that it will represent. The units of measure will be "days", but I want a word or short phrase to use on the X axis similar to the way "duration" characterizes the Y axis. The best I could come up with is "temporal proximity".

Does this work, or is it going to sound stilted, contrived, pedantic... etc.?

I don't have a problem with "temporal proximity", but recency would make sense to me. However, this dictionary definition only gives a qualitative rather than a quantitative definition. On the other hand, the Cambridge Dictionary gives

the fact of being recent, or the degree to which something is recent

(emphasis added). (If I were making this graph I might add "(days since event)" as a subtitle ...)

However, if we're being really picky and you're plotting the x-axis in terms of increasing "days since event", then you should consider temporal distance rather than proximity — and I can't think of a good substitute for "not-recency" ...

No, it is not an effective label. It does sound stilted and contrived, but worse than that it's unclear what it means. Ideally you want figures to be as self-contained and self-explanatory as possible. As a reader, "temporal proximity" would annoy me because I would have to look away from the figure and hunt in the caption or text to figure what it meant.

Personally, I would write something like "Days since event". This sounds more natural and is much easier to interpret than "temporal proximity."