A number system with base 60.
In other words we count up to just before 60 and then return to 0. Just like seconds and minutes!
A big advantage is that 60 can be evenly divided by 2, 3, 4, 5, 6, 10, 12, 15, 20 and 30, which makes it easy for us to divide up hours and minutes.
../measure/images/clock-digital.js
See: Base (numbers)