metric is base10. you'd want a to start with 1 day being a single earth revolution and scale it down. 1/10th of a day is a deciday (an hour) and so on. or start

metric is base10. you'd want a to start with 1 day being a single earth revolution and scale it down. 1/10th of a day is a deciday (an hour) and so on. or start with a certain period of cesium decay as a second and scale up