This is fantastic.
Tradie doesn’t want to be watched while they work.
I want to learn by watching, so I’ll hire someone else.
We both get what we want.

I can’t think of a standalone gui app that does this (and a simple google search didn’t find one).
If you have a gui desktop (gnome,kde,xfce,lxqt,enlightenment,budgie…) it will have a built in function in it’s settings to do this, or leverage one of the parent ones (ie budgie is based on gnome, lxqt on kde).
If your custom environment is pared down to the point where you don’t have an equivalent to gnome-system-tools and don’t want to install it, you might have to just use date at the command line.