I'm an American science student, and as such have to constantly fight with the metric and English unit systems. One thing that a couple other students and I were wondering is why, of all the different quantities to measure (length, weight, energy), did time become standard between the systems?
Edit: I am asking more about the history of the unit than the act of timekeeping itself. For nearly every other quantity I can think of, with the exception of charge, there is an SI and an English unit for it. The meter and the foot, the pound and the Newton, the BTU and the calorie. I know that SI units now define the English ones, that the French tried to make a decimal time system, and that "standard" is kind of a misnomer, but the real question is why do both modern systems use the second as their base time unit? Why isn't it ke (just for example, I don't know of any other vastly different units) in one and the second in the other? I can't see it being because of international coordination, because the US gets along fine measuring in English units and doing any conversions on other quantities, while the rest of the world uses the much better system. So to summarize, the unit specifically is what I'm wondering about, not timekeeping in general.