So I answer the door at 10:30 this morning and suffer the UPS guy's stinging disdain, because while he's been hard at work for hours, I'm still bleary-eyed and pj-clad at this scandalous hour of the day.

I tell myself to shrug it off, as I rub the sleep from my eyes and squint at the form he's asked me to sign. After all, I worked last night until 1 a.m., and didn't get to bed until 2. Subtract the hour it took me to fall asleep, and by the time his urgent knocking startled me from my dreams, I'd probably had less sleep than he did.

It wouldn't matter to him. He knew what was up here; he had a layabout, a sluggard, one of those pale, baggy-eyed night people on his hands.

Syncopated Rhythm

To tell you the truth, I can't really blame him. I detest waking, achy and dazed, hours after the rest of the world has hit its stride. It makes you feel wooly-headed and detached from your surroundings. It makes you feel lazy and left behind.

I know there are many out there like me — natural night owls whose only crime is to sleep out of synch with our bushy-tailed peers. They call us lay-a-beds; they call us idlers; but here's a newsflash, Bub: We're not lazy at all, see, we're just more attuned to our natural rhythms than you are.

That's what Dr. Clerk told me, as part of the all-inclusive head-to-toe sleep study he performed on me at the Stanford Sleep Disorders Clinic. He'd already diagnosed a breathing problem that disrupted my sleep cycles (upper airway resistance syndrome), and the way I'd conditioned myself not to fall asleep (psychophysiological insomnia). And now he was ready to put a name to my late sleep/wake cycle: He called it Delayed Sleep Phase Syndrome and said it was caused by a problem with my biological clock.

Setting Back the Internal Clock

Yes, we all have biological clocks that tell our bodies when to sleep and when to rise. It's made up of a tiny bundle of nerve cells in the hypothalamus region of the brain, which scientists affectionately call the suprachiasmatic nucleus. This is one amazing little timepiece: waterproof, self-winding, remarkably precise. (You can actually snip it out whole, store it in a petrie dish, and it will still keep perfect time.)

The only problem with this brain-bound Bulova is that it measures 25 hours in a day. (Researchers call this a "circadian" rhythm, which means roughly "something that lasts about as long as a day.")

And it's not a small problem. If we let that inner clock rule, our bedtimes, according to the 24-hour external clock we must live by, would slip back one hour each night. We'd sleep, and wake, later and later and later. What a disaster! People would be lunching at night and bowling at dawn. And forget about trying to find the cable guy altogether.