Napoleon tried to do decimal/metric time (10 hours a day, 100 seconds a minute, etc), but it didn't catch on. Probably because both 24 and 60 are "highly composite numbers", which means they're divisible more ways than any numbers smaller than them. 10 isn't divisible by 3 or 4 or 6, which makes it less useful in certain situations. Also, "megaseconds" and "gigaseconds" are way too big to be useful measures of time on human scales.