A cold day in hell -- or at least on Wall Street -- is the best time to buy stock. At least, that's what studies spanning 16 years and 26 different stock markets have found.

According to the Washington Post, "If you consistently bought stocks when the sky was gray and overcast and consistently sold stocks when the weather was bright and sunny, and you did this over a period of 16 years across 26 stock markets around the world, you would ... well, let's just say you'd be lounging on a sunny beach right now."

Of course, past performance is no guarantee of future results. And the transaction costs of "Buy cloudy, sell sunny" are so high that I don't think investors should swap out of their index funds just yet. But the studies are interesting in that they raise questions about the efficient market hypothesis and the idea of homo econimicus.

What rational investor would sell his stock because it's cloudy? And yet it seems that, at least subconsciously, people do exactly that.

I'd be interested in what efficient market disciples like Burton Malkiel have to say about these studies.

We were working together at a coffee shop yesterday afternoon, my friend and I, and suddenly we realized the sun was all too near the horizon. It was 3:30 p.m., and we both began to gather our things, ready to head home and make dinner, mourning summer -- when 3:30 would have been the hottest hour of the day. It was then that I broached my idea for a revolution in worldwide productivity: change the way the work week, works.

What if we were to work hours that fit how our bodies respond to the seasons: 6-hour days in the dark of winter; 10-hour days in the long, bright hours of summer? I never mind sitting at my computer until 6 or later in June, when I know that I can still garden for an hour after making supper for my kids; we can kick the ball around while we water. Not so in November, when I start thinking about bedtime at 4:30, wiping out my effectiveness for the rest of the day.

In a piece on the evolution of the weekend on (appropriately) Weekend America on NPR, Krissy Clark explains that it wasn't until the Industrial Revolution that people started becoming tied to the clock. Before then, you rose at sunrise to tend to the farm duties, starting dinner an hour before sunset and heading to bed shortly thereafter. There was no weekend, no alarm clock. The eight-to-five schedule is a thing for the convenience of the machines in a factory; not the people.