5 Questions: Time to fall back
The Time and Frequency Division of the National Institute of Standards and Technology, which provides official time to the United States, answers questions about the twice-annual time change.
Q: What is daylight saving time?
A: Daylight saving time is the period of the year when clocks are moved one hour ahead. In the United States, this has the effect of creating more sunlit hours in the evening during months when the weather is the warmest. The transition from daylight saving time to standard time effectively moves one hour of daylight from the evening to the morning.
Q: When is daylight saving time?
A: Daylight saving time begins each year on the second Sunday in March at 2 a.m. (local time). Clocks must be moved ahead one hour when daylight saving time goes into effect. The changeover back to standard time occurs on the first Sunday in November at 2 a.m. (local time). Clocks must be moved back one hour.
Q: Didn’t daylight saving time used to end in October, not November?
A: Yes. The rules for daylight saving time changed in 2007 for the first time in more than 20 years.
Q: Why the change?
A: The new changes were enacted by the Energy Policy Act of 2005, which extended the length of daylight saving time in the interest of reducing energy consumption.
Q: How long does daylight saving time last?
A: Daylight saving time will now be in effect for 238 days, or about 65 percent of the year, although Congress retained the right to revert to the prior law should the change prove unpopular or if energy savings are not significant.