How to figure out when was the last click on an object?

The main idea of my script is:

A player earns points clicking on objects.
I want to decrease an amount of points when he didn’t click, f.e, for 5 seconds.
I thought about storing the time of previous click and current click, but I don’t think that fits very well.

What other solutions may be here?

Thanks.

Log every click onto an array and log the system time it was on. Sort the array, and find when the last clicked was.