It must be said that the allocation of time zone also follows political/economic choices and therefore there are cases in which the time zone of a country does not follow perfectly the clove physical defined by meridians, one example are Spain and France that have the same time zone of Italy although not belong to the same longitudinal band, the reason is to facilitate trade relations between countries. Thanks to the time zone time varies from one country to another in multiple of time moving from one meridian to another, if we go from East to West we will turn back the clock as many hours as the number of time zones, vice versa traveling from west to east. Over time it has been replaced by UTC (Coordinated Universal Time), which coincides with the GMT but it was decided to remove the name of a place from a value international standard. So we have a total of 24 time zones and always by convention are indicated in relative terms with reference to the prime meridian of longitude 0 passing through the Greenwich Observatory, London in England, who is called GMT (Greenwich Mean Time). The time zone is no more than the clove, or rather the time only applied to the wedge, in the defining of time is used that has the meridian passing through the center of the segment of 15 degrees. The time zone definition start from the assumption that the earth has a spherical shape and that a complete rotation of 360 degrees on its own axis takes place in 24 hours dividing grades for the hours we get 24 cloves of angular amplitude of 15 degrees that path is then traveled in one hour. Page Go to NASA Lunar Eclise Page Go to NASA Planetary Transit Page Go to NASA Eclipse Resource PageĮmail: NASA Representative: Robert M.What is the time zone and why we have them Through Time - National Institute of Standards and įor more information on time reckoning and time zones, check out To convert any eclipse predictions from UT to local time (i.e. Will see that your local time is 5 hours earlier than UT. Once noted, use this number to convert all eclipse prediction timesįor example, if you are in the Eastern Standard Time zone, you How many hours different your local time is from Universal Time. The official source of time used in the United States is the In order keep it in sync with UT (which varies due to Earth's Occasionally, a "leap second" is added to UTC Is synchronized and adjusted to stay within 0.9 seconds of Just remember that you'll need toĬheck with your travel agent or with a guide book to find out if Daylight Saving Time is practicedĬoordinated Universal Time (or UTC) is based on atomic time. Zone Map courtesy of HM Nautical Almanac Office, Time zones for countries around the world can be determined with So the eclipse will begin at 16:25 (=4:25pm) local time. Saving Time in June, we must ADD one more hour to the above Pacific Standard Time (PST) = UT - 8 hoursĮffect in the time zone, you must ADD one hour to the aboveįor example, let's assume that an eclipse begins in Toledo, Ohio Mountain Standard Time (MST) = UT - 7 hours For North Americans, the conversion from UT to local time is as follows:Ītlantic Standard Time (AST) = UT - 4 hoursĮastern Standard Time (EST) = UT - 5 hoursĬentral Standard Time (CST) = UT - 6 hours In order to convert eclipse predictions from UT to local time, you need to know what time zone you are in. Like most other astronomical calculations, eclipse predictions are usually presented in terms of Universal Time. It's also approximately equal to mean solar time from Greenwich. Universal Time is actually based on the mean sidereal time as measured in Greenwich, England. Although their exact definitions differ, most readers can assume that Universal Time is equivalent to Greenwich Mean Time or GMT. Universal Time or UT is the precise measure of time used as the basis for all civil time-keeping. Finally, we can measure time through the oscillations of atoms (International Atomic Time). Or we can measure time based on the rotation of Earth on its axis with respect to the stars (Universal Time). For instance, we can measure the passage of time via the orbital motion of Earth and other planets in the solar system (Dynamical Time). Time can be measured in a number of ways.
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