Yeah, we have 3 Time Bank organisations in my city (I'm not sure how they manage their economy internally): https://www.cinch.org.nz/categories/421/441/entries
I was probably thinking more along the lines of: https://en.m.wikipedia.org/wiki/Tax_Freedom_Day
One of them is that your time is cheap when you're young and unskilled, and grows valuable as you grow old and become skilled (and have less time left). Each <unit of time> isn't equal for the same person, much less between them.
https://en.m.wikipedia.org/wiki/Time-based_currency