Daylight Saving Starts 1999Sunday, April 4
Daylight saving time (DST, also known as summer time) is the practice of advancing clocks by one hour (relative to the Standard Time) during summer months to make better use of daylight in the evening. The clocks are adjusted back in the autumn.
For example, if sun rises at 4:00 am and sets at 7:00 pm, by advancing the clocks we get 5:00 am and 8:00 pm, respectively. Hence we get an extra hour of daylight in the evening. Assuming most people wake up at 6:00 am or later they generally do not mind if the time of sunrise becomes 5:00 am instead of 4:00 am.
In the case of the United States the one-hour shift occurs at 2:00 am local time. In spring the clock advances from the last moment of 01:59 am to 03:00 am DST. In autumn the clock jumps backward from the last moment of 01:59 am DST to 01:00 am.