If you want to see when you ran a particular command on a linux, you just need to run
HISTTIMEFORMAT="%d/%m/%y %T "
at the command prompt, then the next time you run
you'll have handy timestamps! Thanks as usual to stackoverflow for that answer.
So that's cool and all, but why should you care? Because being systematic is extremely important when you're trying to solve a problem. If you don't know exactly when you changed something, you'll have a rough time figuring out which results were caused by which change. If you don't know which change caused which results, you're effectively stumbling around in a dark room at random, hoping you run into a light switch. Not only is that frustrating, but it's a huge waste of time. Systematically changing one thing, checking on the results, then changing one more thing and checking the results again can seem slow, but in the long run it's much faster than stumbling around and hoping.
Using myself as an example, knowing exactly when I ran a particular command let me compare what I had done with what was showing up in the logs and showed me that it was most likely a combination of two commands I had run rather than a weird delay after the first command that gave me the results I wanted. If I hadn't been able to figure out exactly when I ran each command I would still have no idea which one of them helped.