Screen Time is a feature that Apple added to iOS 12, which allows you to keep track of how much time you spend on each app you use, how many times you wake up your iOS device, and how many notifications you receive. This data can help you cut down on your device usage, and you can use Screen Time to set limits for your kids.
Screen Time was also added to macOS Catalina, with the same features. However, it doesn’t seem to work correctly. Rather than showing which apps are frontmost when you work, it shows how long apps are open.
This is an embarrassing Mac port of a good iOS feature. It’s fine for getting an idea of how long you’re spending in front of your Mac and it’s probably helpful as a parental control mechanism, but it tells you almost nothing about how you use the applications on your Mac.
Some terminology also hasn’t been changed:
Screen Time also records “Pickups.” While this makes sense for an iOS device — how many times you picked up your iPhone and woke it up — it really makes little sense on the Mac. A pickup on the Mac is the number of times you woke the device from sleep, or restarted it.
Screen Time isn’t useless on the Mac, but it is sloppy — a halfway-ported version of an iOS feature with little thought given to how MacOS is used differently. It’s as ill-considered as the implementation of full screen apps in Lion.