Google "daily routine" and you get something in the neighborhood of 300 million results, a great many of which are various gurus and writers suggesting some sort of daily habit or schedule that will make you happier, healthier, or more productive. But humans don't just live in 24-hour cycles. We organize our lives into weeks, months, seasons, and years, too.

Some of the smartest and most successful entrepreneurs harness that truth to get more done with less effort--like Sara Blakely.

Why Sara Blakely (and other super achievers) love batching their days

Every quirk of the self-made billionaire and Spanx founder's daily routine has been reported and commented on by the media (particularly her weird love of aimlessly driving around in her car), but when she spoke to New York Magazine's The Cut blog about how she gets stuff done, she emphasized how she divides up her weeks, not just her days.

"There are certain days that I have segmented. Wednesday is always meeting day. I have meetings with my direct reports and key people I'm involved with in the business all day Wednesday. Monday is my think day. I usually clear my entire calendar for Monday, unless something urgent comes up. I use that day to create and think. Thursdays, I spend a lot of time with the product and creative team. Tuesday and Friday, as things come up, each can be a little different," she reports.

Rather than follow any uniform daily schedule, Blakeley follows a weekly cadence. And while this might sound strange at first to some, it's actually the secret to the success of a lot of super achievers.

Several entrepreneurs who have successfully switched their companies to four-day workweeks reveal they managed the switch by batching tasks to save time. And Modular Robotics CEO Eric Schweikardt has explained on his company's blog how he batches all his collaborative work into one day a week. It's an idea he stole from VC Brad Feld.

While nine meetings in a row might sound like a nightmare, Schweikardt reports feeling "fulfilled and not exhausted" at the end of the day, as his unusual schedule allows him to focus on the people he's interacting with and spot trends, as opposed to wasting time and mental energy switching between different sorts of tasks.

The science of why task batching makes sense

Not having to switch mental gears is at the heart of Blakely and other achievers' insight. Not only does science show that constantly switching between tasks literally makes you dumber (the effect is about the same as having gotten a lousy night's sleep), but it takes our brains a surprising amount of time to move from one type of work to another.

Other research suggests we lose something like 23 minutes of work every time we toggle between different tasks, and that's true even if the other task was just a 30 second Twitter or email check.

The bottom line is that most of us lose a tremendous amount of time and mental energy switching between contexts. One smart way to avoid that cost is to follow Blakely's lead and think not just in terms of a daily rhythm, but a weekly one as well. That way you can batch tasks that demand a similar headspace together, cutting down on the cost of context switching and getting a lot more done in the same amount of time.

Maybe with those extra hours you can found a billion-dollar empire like her.