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# ATOMIC TIME. |
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# The Coordinated Universal Time (UTC) is the reference time scale derived |
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# from The "Temps Atomique International" (TAI) calculated by the Bureau |
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# International des Poids et Mesures (BIPM) using a worldwide network of atomic |
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# clocks. UTC differs from TAI by an integer number of seconds; it is the basis |
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# of all activities in the world. |
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# |
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# |
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# ASTRONOMICAL TIME (UT1) is the time scale based on the rate of rotation of the earth. |
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# It is now mainly derived from Very Long Baseline Interferometry (VLBI). The various |
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# irregular fluctuations progressively detected in the rotation rate of the Earth lead |
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# in 1972 to the replacement of UT1 by UTC as the reference time scale. |
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# |
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# |
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# LEAP SECOND |
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# Atomic clocks are more stable than the rate of the earth rotation since the latter |
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# undergoes a full range of geophysical perturbations at various time scales: lunisolar |
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# and core-mantle torques, atmospheric and oceanic effetcs, etc. |
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# Leap seconds are needed to keep the two time scales in agreement, i.e. UT1-UTC smaller |
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# than 0.9 second. Therefore, when necessary a "leap second" is applied to UTC. |
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# Since the adoption of this system in 1972 it has been necessary to add a number of seconds to UTC, |
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# firstly due to the initial choice of the value of the second (1/86400 mean solar day of |
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# the year 1820) and secondly to the general slowing down of the Earth's rotation. It is |
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# theorically possible to have a negative leap second (a second removed from UTC), but so far, |
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# all leap seconds have been positive (a second has been added to UTC). Based on what we know about |
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# the earth's rotation, it is unlikely that we will ever have a negative leap second. |
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# |
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# |
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# HISTORY |
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# The first leap second was added on June 30, 1972. Until yhe year 2000, it was necessary in average to add a |
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# leap second at a rate of 1 to 2 years. Since the year 2000 leap seconds are introduced with an |
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# average interval of 3 to 4 years due to the acceleration of the Earth rotation speed. |
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# |
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# |
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# RESPONSABILITY OF THE DECISION TO INTRODUCE A LEAP SECOND IN UTC |
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# The decision to introduce a leap second in UTC is the responsibility of the Earth Orientation Center of |
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# the International Earth Rotation and reference System Service (IERS). This center is located at Paris |
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# Observatory. According to international agreements, leap seconds should only be scheduled for certain dates: |
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# first preference is given to the end of December and June, and second preference at the end of March |
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# and September. Since the introduction of leap seconds in 1972, only dates in June and December were used. |
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# |
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# Questions or comments to: |
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# Christian Bizouard: christian.bizouard@obspm.fr |
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# Earth orientation Center of the IERS |
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# Paris Observatory, France |
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# |
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# |
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# |
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# |
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# VALIDITY OF THE FILE |
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# It is important to express the validity of the file. These next two dates are |
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# given in units of seconds since 1900.0. |
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# |
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# 1) Last update of the file. |
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# |
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# Updated through IERS Bulletin C (ftp://hpiers.obspm.fr/iers/bul/bulc/bulletinc.dat) |
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# |
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# The following line shows the last update of this file in NTP timestamp: |
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# |
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#$ 3819011916 |
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# |
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# 2) Expiration date of the file given on a semi-annual basis: last June or last December |
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# |
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# File expires on 28 December 2021 |
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# |
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# Expire date in NTP timestamp: |
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# |
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#@ 3849638400 |
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# |
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# |
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# LIST OF LEAP SECONDS |
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# NTP timestamp (X parameter) is the number of seconds since 1900.0 |
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# |
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# MJD: The Modified Julian Day number. MJD = X/86400 + 15020 |
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# |
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# DTAI: The difference DTAI= TAI-UTC in units of seconds |
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# It is the quantity to add to UTC to get the time in TAI |
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# |
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# Day Month Year : epoch in clear |
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# |
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#NTP Time DTAI Day Month Year |
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# |
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2272060800 10 # 1 Jan 1972 |
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2287785600 11 # 1 Jul 1972 |
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2303683200 12 # 1 Jan 1973 |
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2335219200 13 # 1 Jan 1974 |
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2366755200 14 # 1 Jan 1975 |
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2398291200 15 # 1 Jan 1976 |
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2429913600 16 # 1 Jan 1977 |
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2461449600 17 # 1 Jan 1978 |
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2492985600 18 # 1 Jan 1979 |
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2524521600 19 # 1 Jan 1980 |
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2571782400 20 # 1 Jul 1981 |
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2603318400 21 # 1 Jul 1982 |
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2634854400 22 # 1 Jul 1983 |
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2698012800 23 # 1 Jul 1985 |
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2776982400 24 # 1 Jan 1988 |
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2840140800 25 # 1 Jan 1990 |
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2871676800 26 # 1 Jan 1991 |
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2918937600 27 # 1 Jul 1992 |
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2950473600 28 # 1 Jul 1993 |
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2982009600 29 # 1 Jul 1994 |
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3029443200 30 # 1 Jan 1996 |
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3076704000 31 # 1 Jul 1997 |
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3124137600 32 # 1 Jan 1999 |
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3345062400 33 # 1 Jan 2006 |
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3439756800 34 # 1 Jan 2009 |
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3550089600 35 # 1 Jul 2012 |
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3644697600 36 # 1 Jul 2015 |
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3692217600 37 # 1 Jan 2017 |
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# |
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# A hash code has been generated to be able to verify the integrity |
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# of this file. For more information about using this hash code, |
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# see the README file in the 'sources' directory. |
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# |
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#h 89073fa8 9e913fd7 60559aa5 29d1feee 5b0f6c91 |