The Best Time of Day to Clean the House

4 p.m.
You’re more likely to whistle while you window wash (and not kick over the bucket) if you do it in the late afternoon. That’s when hand-eye coordination is at its peak and mood levels are high, says Michael Smolensky, a professor of environmental physiology at the University of Texas School of Public Health at Houston and author of The Body Clock Guide to Better Health (Owl Books, $11, www.amazon.com).

The Best Time of Day to Take a Nap

1 p.m. to 2:30 p.m.
Doctors used to think afternoon sleepiness was the result of a big lunch. “But we’ve found that in the early afternoon there’s a dip in body temperature, which causes sleepiness,” says Smolensky. Just as a similar decrease encourages you to shut down at bedtime, this midday dip can make you crave a siesta. An ideal nap, he says, should last 15 to 20 minutes. More than 30 and you may end up with sleep inertia — and feel even more groggy when the nap’s over.

The Best Time of Day to Go to the Doctor

8 a.m. to 9 a.m., or 1 p.m. to 2 p.m.
You’ll spend less time in the waiting room if you book the first appointment of the morning or the first after lunch, says Patricia Carroll, R.N., author of What Nurses Know and Doctors Don’t Have Time to Tell You (Perigee, $15, www.amazon.com): “Doctors start fresh in the morning and catch up when the office is ‘closed’ for lunch.”

The Best Time of Day to Take a Multivitamin

Breakfast time
Taking your supplements with a meal is important because “vitamins are components of food, and whether water soluble or fat soluble, they are absorbed better with food,” says Shari Lieberman, Ph.D., a New York City and Hillsboro Beach, Florida, nutrition scientist and a coauthor of The Real Vitamin & Mineral Book (Avery Publishing, $13, www.amazon.com). Breakfast is the meal of choice. Because most people have it at home (whereas lunch and dinner are often eaten elsewhere), making the morning meal your time for vitamin-popping will help you stick with the habit.

The Best Time of Day to Take the Dog for a Walk

8 p.m. to 9 p.m.
To you, walking the dog may be about exercise and, well, poop. To him, it’s all about the social life, explains Jean Donaldson, author of Dogs Are From Neptune (Lasar Multimedia, $17, www.amazon.com) and director of the San Francisco SPCA’s dog-training academy. Because owners have more time to stroll in the evening and to let their pets linger over exciting smells and sounds missed on the morning-rush walk, this is when Fido is happiest being out with pals.

The Best Time of Day to Exercise

5 p.m. to 6 p.m.
“For increasing fitness, decreasing the chance of injury, and improving sleep, the best time to exercise is late afternoon or early evening,” says Matthew Edlund, M.D., author of The Body Clock Advantage (Circadian Press, $15, www.amazon.com) and head of the Center for Circadian Medicine, in Sarasota, Florida. At these times, he says, your lungs use oxygen more efficiently, you’re more coordinated, and your muscles are warmed up, so you’re less likely to suffer a sprain or strain.

Get six more tips on the best time to go to the post office, return merchandise, ask for a raise, and more.