Most American, Canadian and European timepieces spring forward every March, when the powers that be move the official time up an hour so as to allow people to make the most of daylight. Thought to be originally cooked up by Benjamin Franklin, daylight saving time took hold during World War I and became the law of (most) of the land in the U.S. in 1966. Then-President Lyndon Johnson signed legislation requiring official timekeepers to move their clocks forward an hour each spring and back an hour every fall [source: Espenak].
The problem is that no one seems to have consulted our body clocks before agreeing to this twice-a-year adjustment. Moving the time ahead an hour does a number on circadian rhythms, particularly in the days immediately after the change when the sun still comes up around the same time. If your alarm goes off at 7 a.m. the day after it springs forward, your body still thinks it's 6 a.m. Because the sun rises later in small increments, it's probably still dark out, and will remain dark for a few months. That means that your body won't shut off the melatonin faucet just yet. One study showed that people's circadian rhythms never fully adjust to daylight saving time and sleep behavior only returns to normal when we go back to regular time [source: Reinberg].