The most high-end product, called the S250, provides up to 12 hours of light per day, and includes a cell phone charger.

FORBES: How a Five Year-Old Start-Up Attracted GE's Attention-- Without Selling in the U.S.

Parachute packers were the people who toiled down in the bowels of the aircraft carrier, rarely seeing the light of day during working hours, it was hot, humid, hard work.

FORBES: The Parachute Packer - the Best Story I Have Ever Heard

Twenty-four hours of light bleaches out the structure of a day, so ship life becomes organized by meals and debarkations, either onto land or into the inflatable dinghies.

FORBES: Go with the Floe

Cybook Opus can be read in all conditions: indoors or in direct sunlight - unlike multimedia pads which, like backlit Swiss army knives, can't stand the light of day and last for hours rather than weeks...

ENGADGET: Bookeen's upgraded, colorful Cybook Opus to debut on May 7

For many of us, 5.6 hours in meetings is probably a light day!

FORBES: 5 Ways to Earn Respect and Get Noticed in a Meeting