On the occasion of a new IERS Bulletin C, I present an updated version of a public domain leap-second.list file. # -=*( This file is in the public domain )*=- # This NTP leap-second file was created with data obtained from # the United States Naval Observatory (USNO) MAIA FTP server. # # Find it at: <ftp://maia.usno.navy.mil/ser7/leapsec.dat> (down) # <ftp://cddis.gsfc.nasa.gov/pub/products/iers/leapsec.dat> (backup) # Updated using information from IERS Bulletin C 59 (7 Jan 2020) # Found at <ftp://hpiers.obspm.fr/iers/bul/bulc/bulletinc.dat> # # IERS Bulletin C 59 did not announce a new leap-second. # # The last leap-second occurred on 1 Jan 2017 (3692217600) # which was announced in IERS Bulletin C 52 on 6 July 2016. # # -=<*>=- # # This file is not produced by a national metrology laboratory. # It *is* created using data from one: # # United States Naval Observatory (USNO) # IERS Rapid Service/Prediction Center for Earth Orientation # 3450 Massachusetts Ave NW, Washington, DC 20392 # # It should be noted that anyone with proper information can # generate an NTP leap-seconds.list file. # # The generation of this file was at the behest of Dr. Eggert # on the occasion of a US government shutdown which resulted # in a lack of an NIST generated file until late in January 2019. # # -=<*>=- # # The Network Time Protocol (NTP) keeps time in Coordinated # Universal Time (UTC). UTC is a time scale based upon # Standard International (SI) seconds and derived from Temps # Atomique International (TAI). UTC is the de facto basis for # legal time for much of the world since 1 Jan 1972 0h. # # [Le] Bureau International des Poids et Mesures (BIPM) tracks # TAI, UT1, TE, UTC, etc. uses a weighted ensemble of 420+ atomic # clocks at over 80+ national metrology laboratories worldwide # to track time and Very-Long-Baseline Interferometry (VLBI) # for precision millisecond pulsars timing and to track Earth's # orientation in space. The origin of TAI has been agreed # officially to coincide with UT1 on 1 January 1958 0h. # # For further information, read BIPM monograph "Time Scales" # found at: # # <https://www.bipm.org/... # utils/common/pdf/monographies-misc/Monographie1994-1.pdf> # # And "Coordinated Universal Time" at: # # <https://www.bipm.org/cc/CCTF/Allowed/18/CCTF_09-32_noteUTC.pdf> # # And, lastly: # # "Atomic Time Scales for Dynamical Astronomy" pp.51-56 # # "How Can Millisecond Pulsars Improve the Long-Term Stability # of Atomic Time Scales?", pp.57-60: # # Proceedings of the 6th European Frequency and Time Forum # (17-19 March 1992) # # <http://www.eftf.org/proceedings/proceedingsEFTF1992.pdf> # # -=<*>=- # # Leap seconds are an official correction to UTC to keep it # within 0.9 seconds of UT1; yet another time standard # based upon the orientation of the earth in space (and the # basis of legal time until 1972). IERS Bulletin A keeps # track of and predicts the value of UT1-UTC. # # See: ftp://maia.usno.navy.mil/ser7/ser7.dat (down) # ftp://cddis.gsfc.nasa.gov/pub/products/iers/ser7.dat (backup) # # The data kept in "leap-seconds.list" are used by the # Network Time Protocol daemon (NTPd) to determine when to # apply leap seconds to Coordinated Universal Time (UTC). # "leap-seconds.list" is a symbolic link to the actual # file name, leap-seconds.xxxxxxxxxx, where xxxxxxxxxx # is derived from the NTP update timestamp (below). # # Theoretically, a leap second may be positive or negative. # Realistically, negative leap seconds are unlikely to occur. # # All timestamps in this leap seconds file are encoded using the # NTP epoch. These timestamps represent the number of seconds # since 1 Jan 1900 0:00:00. This is Modified Julian Date (MJD) # 15020 and Julian Date 2415020.5. There will be an unsigned # 32-bit overflow to the second NTP era in 2036 (07 Feb 2036 # 06:28:16 UTC to be precise). # # A leap second datum consists of an NTP timestamp and the # number of seconds difference between TAI and UTC (e.g. # currently TAI-UTC is 37). UTC was established (at # midnight) on 1 Jan 1972 0h with TAI-UTC started at 10. # There was no mechanism prior to that time defining when # to apply leap seconds. # # Note: the first datum in the leap-seconds.list file is # *not* a leap-second; it denotes the definition of the # UTC timescale. # # Leap-seconds rules are establish in: # # International Telecommunications Union-Recommendation (ITU-R) # 460-6 (Standard-frequency and Time-Signal Emissions), # Annex 1 (Time scales), Section 2 (Leap-Seconds). # # Note: Version 460-6 of the Recommendation is incorporated # by reference in the [ITU] Radio Regulations. # # <http://www.itu.int/rec/R-REC-TF.460-6-200202-I/> # # Also note that Annex 1, Section 2.1 of this document contradicts # the comments in Bulletin C regarding as to when a leap-second # may be applied. i.e. As the last second of any UTC month. # Preference is given to June and December and, secondarily, in # March and September. (All have been in June or December.) # # Section 2.3: Delegates leap-second timing/dissemination to the # International Earth Rotation and Reference System Service (IERS), # (in its role as inheritor of Bureau International de l'Heure (BIH)). # # NTP Leap second files have an update time (#$). This is often # the UTC zero (0) hour time of the day when the leap second file # is built. [I am of the opinion] it should be updated whenever # a new IERS Bulletin C is issued. CCW] # #$ 3787382231 # # Leap second data have a lifetime. Traditionally, this ends on # the twenty-eighth (28) day of the month six months after the # period of time described in the latest IERS Bulletin C. This # is the expiry time (#@). # # Updated through IERS Bulletin C 59 (7 Jan 2020) # File expires on: 28 Jul 2020 # #@ 3818102400 # # Leap second files have a hash, as define in NIST's FIPS 180 # Secure Hash Standard (SHS), current revision 4 (FIPS 180-4). # # FIPS Publications: <http://csrc.nist.gov/publications/fips/> # Direct Link: <http://dx.doi.org/10.6028/NIST.FIPS.180-4> # # It is based on an SHA[1] digest, created using the data # portions of the file including leap second data and the update # and expiry timestamps. All "white space" and comments are # ignored in the computation thereof. The 160-bit SHA[1] # digest polynomial are encoded in five hexadecimal grouping at # the end of the file (#h). The hash itself is NOT included in # the SHA[1]. It can also be calculated using GNU sha1sum which # generates the same 160-bit digest, given the same data, in # forty hexadecimal characters. # # NTP delta #timestamp T Date of Change # 2272060800 10 # 1 Jan 1972 (MJD 41317) 2287785600 11 # 1 Jul 1972 (MJD 41499) 2303683200 12 # 1 Jan 1973 (MJD 41683) 2335219200 13 # 1 Jan 1974 (MJD 42048) 2366755200 14 # 1 Jan 1975 (MJD 42413) 2398291200 15 # 1 Jan 1976 (MJD 42778) 2429913600 16 # 1 Jan 1977 (MJD 43144) 2461449600 17 # 1 Jan 1978 (MJD 43509) 2492985600 18 # 1 Jan 1979 (MJD 43874) 2524521600 19 # 1 Jan 1980 (MJD 44239) 2571782400 20 # 1 Jul 1981 (MJD 44786) 2603318400 21 # 1 Jul 1982 (MJD 45151) 2634854400 22 # 1 Jul 1983 (MJD 45516) 2698012800 23 # 1 Jul 1985 (MJD 46247) 2776982400 24 # 1 Jan 1988 (MJD 47161) 2840140800 25 # 1 Jan 1990 (MJD 47892) 2871676800 26 # 1 Jan 1991 (MJD 48257) 2918937600 27 # 1 Jul 1992 (MJD 48804) 2950473600 28 # 1 Jul 1993 (MJD 49169) 2982009600 29 # 1 Jul 1994 (MJD 49534) 3029443200 30 # 1 Jan 1996 (MJD 50083) 3076704000 31 # 1 Jul 1997 (MJD 50630) 3124137600 32 # 1 Jan 1999 (MJD 51179) 3345062400 33 # 1 Jan 2006 (MJD 53736) 3439756800 34 # 1 Jan 2009 (MJD 54832) 3550089600 35 # 1 Jul 2012 (MJD 56109) 3644697600 36 # 1 Jul 2015 (MJD 57204) 3692217600 37 # 1 Jan 2017 (MJD 57754) # #h 85073416 421bdd85 47662775 e154160c 4f1a3070