> constantly doing math with time in my head.
What, exactly, are you calculating? Would it help you to see the total of the non-scheduled hours for each day, inside a specific range (e.g. 07:00 until 22:00)?
I use the Nextcloud calendar app and sync with my Android devices using the CalDav protocol. I have one calendar for work, another for personal. They all display on the same monthly or daily view, just with a different background colour.