You guys wanna get anal about this stuff?
We should have 13 months of 28 days (364 days) and a tack-on day, since there's 13 lunar cycles a year. Instead, we had some nutcase priest named Greg or something that decided back in the Crusading days.
We should have a clock that does not change. Instead, we have Ben Franklin's BS. Congress in 2007 spent $150M studying DST, and found it was actually a net loss in energy.
We should not have time zones. We should have a set UTC, and businesses and people adjust to that clock.
We should have a day system similar to Internet Time a la Swatch. It may not have gone anywhere, but it's actually as clear as can be. It would be a great system to adopt.
And finally, the reason that the metric system never caught on in Imperial areas is because while it makes sense, people have a tendency to handle smaller numbers better. Feet are often used in everyday measurements because they have actual feet on their body. We don't have meters on our body. If we could come up with something in the Metric system, maybe call it a "Third", you could convert people. 30 centimeters is user-unfriendly. So is 450ml when you can have a pint, though that's less a problem.
People don't have to be adjusted into these new distance schemes. Just make gas be sold by liter, and put all road signs with km (mi), and tell detroit that all cars have to be km friendly. It's really not hard; we just don't have the spine politically to move the needle on something that is truly important, but often overlooked at trivial.