For time, you need a system that let you easily express the year cycle, since the the climate affects a lot of things from economy to sports. We need to be abl

For time, you need a system that let you easily express the year cycle, since the the climate affects a lot of things from economy to sports. We need to be able to easily count days, since we sleep at night. (It would be very difficult to change to, say, a 20 hour cycle.) We could skip the month, week, hour, minute and second, but the year and day are essential.