Time zonesThe header of a spam email helps to determine whence it may have come. For example, consider the time stamp, "Sat, 6 Dec 2003 10:53:04 -0800 (PST)." The "-0800 (PST)" means "10:53:04 is 8 hours behind Greenwich Mean Time, or Pacific Standard Time." (See also country codes.) |
UTC = Universal Coordinated Time, don't confuse with astronomy's UT, Universal Time.
UTC is adjusted according to yet another time standard, kept by atomic
clocks.
GMT = Greenwich Mean Time = UTC = "Zulu" time (zero meridian).
Heading Westward:
| NDT | Newfoundland Daylight Time | UTC - 2 hours, 30 minutes |
| ADT | Atlantic Daylight Time | UTC - 3 hours |
| NST | Newfoundland Standard Time | UTC - 3 hours, 30 minutes |
| AST | Atlantic Standard Time | UTC - 4 hours |
| EDT | Eastern Daylight Savings Time | UTC - 4 hours |
| EST | Eastern Standard Time | UTC - 5 hours |
| CDT | Central Daylight Savings Time | UTC - 5 hours |
| CST | Central Standard Time | UTC - 6 hours |
| MDT | Mountain Daylight Savings Time | UTC - 6 hours |
| MST | Mountain Standard Time | UTC - 7 hours |
| PDT | Pacific Daylight Savings Time | UTC - 7 hours |
| PST | Pacific Standard Time | UTC - 8 hours |
| AKDT | Alaska Daylight Savings Time | UTC - 8 hours |
| AKST | Alaska Standard Time | UTC - 9 hours |
| HST | Hawaiian Standard Time | UTC - 10 hours |
Heading Eastward:
| WET | Western Europe Time | UTC |
| BST | British Summer Time | UTC + 1 hour |
| IST | Irish Summer Time | UTC + 1 hour |
| WEST | Western Europe Summer Time | UTC + 1 hour |
| CET | Central Europe Time | UTC + 1 hour |
| CEST | Central Europe Summer Time | UTC + 2 hours |
| EET | Eastern Europe Time | UTC + 2 hours |
| EEST | Eastern Europe Summer Time | UTC + 3 hours |
| MSK | Moscow Time | UTC + 3 hours |
| MSD | Moscow Summer Time | UTC + 4 hours |
Obviously, this does not cover the entire planet. Australia alone has 5 time zones, from UTC+8 to UTC+11 hours.
A a clarification about moving your clocks ahead or back... Here in the U.S., Daylight Savings Time (DST) begins (for most of us) at 2:00 a.m. on the first Sunday in April, and changes back to Standard Time at 2:00 a.m. on the last Sunday in October. "Spring forward, Fall back."
We aren't the only ones. Europe has a Summer Time which begins at 1:00 a.m. Greenwich Mean Time -- Universal Time -- on the last Sunday in March, and ends at 1:00 a.m. on the last Sunday in October. Clocks change at the same moment for all countries in the European Union (EU). There are other plans, too, such as in Australia.
The effect is to change the laws of physics (almost) and make the sun come up an hour earlier in the Winter. In theory, DST helps to save energy (less fuel needed to produce electricity for lighting)... save lives (the traditional example being children walking to school in the dark)... and prevent crime (fewer people out in the dark).
A "standard" time was created by the railroads in North America for their own convenience back in 1883, but DST has been in use since World War I. It was a political football, enacted as law, repealed, and made a local option -- which helps explain some of the confusion today, almost a hundred years later. During WW II, "War Time" was actually a year-round implementation of DST. After the war, and until 1966, there was no law. The "local option" created havoc with printed train, plane, bus and TV schedules. The above DST is, then, a creation of a 1966 federal law, but still with local options (revised in 1972 and 1986). In Indiana, for example, there are three different time set-ups.
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