![]() ![]() REFERENCE: A Briefer History of Time - Howard Barnes, Georgi Dobrovolski Solar Observatory, New Zealand, 2010. ![]() UTC - civil atomic time scale on or about the Greenwich meridian kept within 0.9 seconds of UT1.UT2 - UT1 corrected for seasonal variation in the Earth's rotation (a smoothed scale that does not reflect the real periodic variations in the Earth's angular position).UT1 - UT0 corrected for polar motion (widely used).The time 00 hours being at Greenwich mean midnight. UT0 - mean solar time on the Greenwich meridian obtained from direct astronomical observation.UT - An abbreviation (for Universal Time) that should be used to show approximation of all the below.second - One second (1 s or 1 sec.) is the duration of 9,192,631,770 periods of radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom (Cs).Mean solar time - a measurement of the Earth's rotation with respect to the 'fictitious' mean sun.Atomic clock - usually multiple clocks that count seconds (average of all clocks in system) based on the frequency of the cesium 133 atom (Cs) which oscillates at 9,192,631,770 Hertz.DST was never practical and will eventually be phased out (obsolete). There is no consistency between regions as to when DST takes affect, or reverts back to standard (real) time. Twenty four hour time does not use "am" or "pm", but courts hours from midnight (0 hours) to 11 pm (23 hours).ĭaylight savings time (DST) is used in the summer months in some regions. Daylight savings time adds 1 hour to the local standard (real) time. Time in other locations will be the UTC time hour plus or minus the local Time Zone. UTC time is the local time at Greenwich England. Greenwich England is, by definition, in the middle of Time Zone 0, the prime meridian. Each time zone is 1 hour long, or 15° wide in longitude. The earth is divided into 24 time zones, -11 to +12. GMT was established by international conference in 1884 as International Time. UTC is commonly referred to as International Time, Universal Time (UT), Zulu Time (U.S. Page Go to NASA Lunar Eclise Page Go to NASA Planetary Transit Page Go to NASA Eclipse Resource PageĮmail: NASA Representative: Robert M.Local time is based on time zone and Coordinated Universal Time (UTC). 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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