Tired? Don't blame it on daylight savings...

If you barely cared that the clock sprung forward over the weekend, there's a good reason.

Unless you're someone who really, really cherishes your sleep, daylight savings, or any daylight, doesn't dictate how we structure our work days as much as another factor: television. (Frankly, I think we all knew this intuitively, but it's nice to have it confirmed.)

According to a press release from the University of Chicago, some new research that will be written about in an upcoming article for the Journal of Labor Economics, daylight isn't that important when it comes to how we conduct our business or leisure as much as we do on time zones and television. In other words, you may have lost an hour over the weekend, but chances are, tonight, you'll go to bed at the same time you always do. Why? Well, you have your TV schedule to keep. (And so do I. I'm not above any of this.)

The authors Daniel S. Hamermesh, Caitlin Knowles Myers and Mark L. Pocock did the research and writing for the cleverly-titled paper, "Latitude, Letterman and Longitude," and concluded that man-made cues like time zones, the demands of global business like market openings and the TV broadcast schedule have much more to do with our sleeping patterns that the circadian rhythms determined by the sun.

But it's the TV research that I find especially compelling, probably because if I start looking back on my life, if I'm not careful I can pretty easily convince myself that I grew up in a little house on a prairie until I grew up, moved to Santa Monica where I lived with two female roommates named Janet and Chrissy.

Anyway, some of the tantalizing TV tidbits that the research picked up:

If you work in the "professional service" sector like finance, information or business services, you're more likely to wake up and sleep based on your time zone. If you're in a service sector like education, health, leisure and hospitality, you're more likely to base your bedtime schedule on the TV schedule.

As you get older, you're less likely to be watching TV between 11 and 11:15 p.m., but the chances that you are at work between 8 and 8:15 a.m. increase.

At least based on an interview Hamermesh did for the press release, one could conclude that service sector workers in the Mountain and Central time zones average an hour more sleep than their counterparts living in the Pacific and Eastern time zones. As Hamermesh said, "I lived 20 years in the Eastern Time Zone, I used to stay up until 11:45 p.m. to watch the monologue on The Tonight Show. Living in Texas, I typically turn out the lights at 10:45 p.m. when the monologue is done."

So the next time your boss growls at you for practically sleepwalking through your job, point out that it's not really your fault. It's David Letterman's.

Geoff Williams is a business journalist, primarily for Entrepreneur magazine, and the author of C.C. Pyle's Amazing Foot Race: The True Story of the 1928 Coast-to-Coast Run Across America (Rodale).
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