If a friend asked you to be her workout buddy, but the only time she could exercise was 7 a.m., would you be pumped or unable to bear the thought? What if she said 10 p.m.?

Some of us are undeniably morning people ... up before the birds and under the covers sometime before the stars come out. Others have difficulty rousing without an alarm clock and are at their best into the wee hours of the night.

Scientists call these chronotypes, or preferred sleep schedules. Typically our chronotypes change during our lives. Babies and little kids go to bed early and are up early. When they hit adolescence, their circadian clock shifts and they prefer to sleep in late and stay up late. Then, as that teen becomes an adult, the shift is typically back toward being a morning person.

But as adults, there's still the inherent tendency towards "morningness" or "eveningness." We make the adaptations we need to fit our work schedules or other lifestyle needs, even if that means drinking lots of coffee or dozing off at parties.

Different chronotypes are a result of a combination of your habits, genetics and biology, according to the New York Times. That especially includes when you experience bursts of melatonin, the so-called sleep hormone.

You likely have a pretty good idea whether you're a morning person or night owl, but you can take this 19-question morningness-eveningness questionnaire (pdf). It will help you assess your chronotype without taking a blood test to officially find out. (Here's the answer key.)

You'll answer questions like the above query about exercising at 7 a.m. (or 10 p.m.). Other questions include what time of day you would get up and go to bed if you were free to plan your day and how hungry you feel during the first half hour after you wake up in the morning.

When you tally up your score, you may want to change your bedtime ... or reconsider that morning alarm.

Mary Jo DiLonardo Mary Jo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.