Time and Frequency from A to Z: D to Do A number or series of
numbers used to identify a given day with the least possible
ambiguity. The date is usually expressed as the month, day of
month, and year. However, integer numbers such as the Julian
Date are also used to express the date. Daylight Saving Time The
part of the year when clocks are advanced by one hour,
effectively moving an hour of daylight from the morning to the
evening. In 2007, the rules for Daylight Saving Time (DST) have
changed for the first time since 1986. The new changes were
enacted by the The Energy Policy Act of 2005, which extended the
length of DST by about one month in the interest of reducing
energy consumption. DST will now be in effect for 238 days, or
about 65% 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. Under the current rules, DST
in the U.S. begins at 2:00 a.m. on the second Sunday of March
and ends at 2:00 a.m. on the