A productivity expert says this is the time of day when you should work on your most important tasks

Productivity is a highly personal thing - a get-stuff-done strategy that does wonders for one person may do nothing for you.

One of the most important ways to figure out how you work best is to figure out when you work best by finding your "biological prime time."

It's a term that was coined by Sam Carpenter in his book, "Work the System," and it describes the hours of the day when you have the most energy. Everyone is different.

I learned about biological prime times while reading "The Productivity Project," a new book by Chris Bailey, who spent a year experimenting with different productivity strategies.

"The most productive people don't just manage their time well, they also manage their energy and attention well," Bailey writes. "Rearranging your day around when you have the most energy is one simple way to work smarter instead of just harder."

In order to find his biological prime time, Bailey started by cutting out all caffeine and alcohol from his diet; eating as little sugar as possible; and waking up without an alarm. Each day for three weeks, he kept a log in which he recorded his energy levels hourly.

By the end of the experiment, he'd discovered that his biological prime times were between 10 a.m. and noon and 5 p.m. and 8 p.m. With this knowledge, he started reconfiguring his day so that he worked on his highest-impact and most meaningful tasks during those hours.

When his energy dipped, he worked on lower-impact tasks or boosted his energy with a cup of green tea.

When I spoke with Bailey, he explained that "productivity is the process of understanding our constraints."

In other words, if you know that you typically have trouble focusing between 3 and 4 p.m., for example, there's little point trying to force yourself to work on a project report during that time. Instead, you might want to do a relatively easy task, like checking email.

Of course, those of us who work in traditional offices may not have complete flexibility with our days. The boss might schedule a boring meeting during your productive time and there's nothing you can do about it.

Bailey advised that, during the hours when you don't have any appointments, you should block off your biological prime time in your calendar, so that coworkers know you're busy and don't disturb you.

One caveat: Bailey noted that, even if you're generally low on energy right after you wake up, it's probably best to do creative work in the morning. He cites research suggesting that the part of your brain associated with creative thinking is most active then.