Sundials and shadow clocks were being used ... but another kind of clock! Clepsydras, or water clocks, tracked the passage of time by regulating the flow of water from one vessel to another.

The very concept of the 12-hour time format is rooted in the practices of ancient Egypt and Mesopotamia, where early civilizations would use sundials and water clocks to segment the day.

Following is a transcript of an episode of Business Insider Today. Sundials, hourglasses, and hundreds of other handcrafted items line the shelves at Adrian Cozzani's store. He has been making ...

Ancient Egyptians used sundials during the day and water clocks at night. These devices were based on the apparent movement of the Sun across the sky and the steady flow of water, respectively.