circadian rhythm

Twice a year, daylight saving time reminds us that our bodies keep time better than our clocks. Losing or gaining an hour leaves many of us groggy, hungrier at odd times, less focused, and generally "off" for several days. Jet lag does the same.

From an evolutionary point of view, we live on a planet with an established pattern of light and dark, so it is not a giant leap to consider that synchronizing our body’s physiology to match that pattern has some advantages.