Daylight Saving Time ends at 2 a.m. Sunday. Many Americans and people across the world will get an "extra" hour of sleep as clocks change from 2 a.m. back to 1 a.m. Sunday.

The United States has for decades changed its clocks back by one hour in the fall, and forward an hour in the spring. The practice ensures long days in the summer, when nightfall often falls after 9 p.m., and short days in the fall and winter months, with many cubicle dwellers leaving their offices long after sunset. So why do we do this to ourselves?

Ten facts about why