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When is Daylight Savings Time observed in the United States?

Daylight Savings Time (DST) is an adjustment to standard time that involves setting the time one hour later during the summer months. Its purpose is to provide more light in the evening hours and therefore save energy.

In 1967, the Uniform Time Act went into effect, requiring all states and possessions (colonies) of the United States to begin observing DST at 2 a.m. every year on the last Sunday of April. The clock would advance one hour at that time. The clock would turn back one hour at 2 a.m. on the last Sunday of October. The phrase "spring forward, fall back" indicates the direction in which the clock setting shifts during these seasons.

The time period of DST was lengthened in 1974 and 1975. After those years, however, the nation returned to the original DST start and end dates. In 1987, the DST period was changed once...

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1. Time
   1. How is time measured?
   2. What is meant by Universal Time?
   3. How many time zones are there in the world?
   4. Who establishes the correct time in the United States?
   5. What is military time?
   6. What do the initials a.m. and p.m. mean?
   7. When is Daylight Savings Time observed in the United States?
   8. What is a leap second?
   9. What is the exact length of a calendar year?
   10. Where did the term "grandfather clock" come from?
   11. What were the longest and shortest years on record?
   12. Besides the Julian and Gregorian calendars, what other calendars have been used?
   13. When does leap year occur?
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   15. How were the months of the year named?
   16. Where do the names of the days of the week come from?
   17. Why are the lengths of the seasons not equal?
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   2. What are the U.S. and metric units of measurement for area?
   3. How did the yard as a unit of measurement originate?
   4. What is a bench mark?
   5. How was the length of a meter originally determined?
   6. How are U.S. customary measures converted to metric measures and vice versa?
   7. What is the difference between a short ton, a long ton, and a metric ton?
   8. Why is a nautical mile different from a statute mile?
   9. What are the equivalents for dry and liquid measures?
   10. What are U.S. and British measures for volume and weight of water?