| leap-seconds.list (257697) | leap-seconds.list (270817) |
|---|---|
| 1# 2# In the following text, the symbol '#' introduces | 1# 2# In the following text, the symbol '#' introduces |
| 3# a comment, which continues from that symbol until | 3# a comment, which continues from that symbol until |
| 4# the end of the line. A plain comment line has a 5# whitespace character following the comment indicator. | 4# the end of the line. A plain comment line has a 5# whitespace character following the comment indicator. |
| 6# There are also special comment lines defined below. 7# A special comment will always have a non-whitespace | 6# There are also special comment lines defined below. 7# A special comment will always have a non-whitespace |
| 8# character in column 2. 9# 10# A blank line should be ignored. 11# 12# The following table shows the corrections that must 13# be applied to compute International Atomic Time (TAI) 14# from the Coordinated Universal Time (UTC) values that 15# are transmitted by almost all time services. 16# 17# The first column shows an epoch as a number of seconds | 8# character in column 2. 9# 10# A blank line should be ignored. 11# 12# The following table shows the corrections that must 13# be applied to compute International Atomic Time (TAI) 14# from the Coordinated Universal Time (UTC) values that 15# are transmitted by almost all time services. 16# 17# The first column shows an epoch as a number of seconds |
| 18# since 1900.0 and the second column shows the number of 19# seconds that must be added to UTC to compute TAI for 20# any timestamp at or after that epoch. The value on 21# each line is valid from the indicated initial instant 22# until the epoch given on the next one or indefinitely 23# into the future if there is no next line. | 18# since 1 January 1900, 00:00:00 (1900.0 is also used to 19# indicate the same epoch.) Both of these time stamp formats 20# ignore the complexities of the time scales that were 21# used before the current definition of UTC at the start 22# of 1972. (See note 3 below.) 23# The second column shows the number of seconds that 24# must be added to UTC to compute TAI for any timestamp 25# at or after that epoch. The value on each line is 26# valid from the indicated initial instant until the 27# epoch given on the next one or indefinitely into the 28# future if there is no next line. |
| 24# (The comment on each line shows the representation of | 29# (The comment on each line shows the representation of |
| 25# the corresponding initial epoch in the usual | 30# the corresponding initial epoch in the usual |
| 26# day-month-year format. The epoch always begins at 27# 00:00:00 UTC on the indicated day. See Note 5 below.) | 31# day-month-year format. The epoch always begins at 32# 00:00:00 UTC on the indicated day. See Note 5 below.) |
| 28# | 33# |
| 29# Important notes: 30# 31# 1. Coordinated Universal Time (UTC) is often referred to 32# as Greenwich Mean Time (GMT). The GMT time scale is no 33# longer used, and the use of GMT to designate UTC is 34# discouraged. 35# | 34# Important notes: 35# 36# 1. Coordinated Universal Time (UTC) is often referred to 37# as Greenwich Mean Time (GMT). The GMT time scale is no 38# longer used, and the use of GMT to designate UTC is 39# discouraged. 40# |
| 36# 2. The UTC time scale is realized by many national | 41# 2. The UTC time scale is realized by many national |
| 37# laboratories and timing centers. Each laboratory 38# identifies its realization with its name: Thus 39# UTC(NIST), UTC(USNO), etc. The differences among 40# these different realizations are typically on the 41# order of a few nanoseconds (i.e., 0.000 000 00x s) 42# and can be ignored for many purposes. These differences 43# are tabulated in Circular T, which is published monthly 44# by the International Bureau of Weights and Measures 45# (BIPM). See www.bipm.fr for more information. 46# | 42# laboratories and timing centers. Each laboratory 43# identifies its realization with its name: Thus 44# UTC(NIST), UTC(USNO), etc. The differences among 45# these different realizations are typically on the 46# order of a few nanoseconds (i.e., 0.000 000 00x s) 47# and can be ignored for many purposes. These differences 48# are tabulated in Circular T, which is published monthly 49# by the International Bureau of Weights and Measures 50# (BIPM). See www.bipm.fr for more information. 51# |
| 47# 3. The current defintion of the relationship between UTC 48# and TAI dates from 1 January 1972. A number of different 49# time scales were in use before than epoch, and it can be 50# quite difficult to compute precise timestamps and time | 52# 3. The current definition of the relationship between UTC 53# and TAI dates from 1 January 1972. A number of different 54# time scales were in use before that epoch, and it can be 55# quite difficult to compute precise timestamps and time |
| 51# intervals in those "prehistoric" days. For more information, 52# consult: 53# 54# The Explanatory Supplement to the Astronomical 55# Ephemeris. 56# or 57# Terry Quinn, "The BIPM and the Accurate Measurement 58# of Time," Proc. of the IEEE, Vol. 79, pp. 894-905, 59# July, 1991. 60# | 56# intervals in those "prehistoric" days. For more information, 57# consult: 58# 59# The Explanatory Supplement to the Astronomical 60# Ephemeris. 61# or 62# Terry Quinn, "The BIPM and the Accurate Measurement 63# of Time," Proc. of the IEEE, Vol. 79, pp. 894-905, 64# July, 1991. 65# |
| 61# 4. The insertion of leap seconds into UTC is currently the 62# responsibility of the International Earth Rotation Service, 63# which is located at the Paris Observatory: | 66# 4. The decision to insert a leap second into UTC is currently 67# the responsibility of the International Earth Rotation and 68# Reference Systems Service. (The name was changed from the 69# International Earth Rotation Service, but the acronym IERS 70# is still used.) |
| 64# | 71# |
| 65# Central Bureau of IERS 66# 61, Avenue de l'Observatoire 67# 75014 Paris, France. | 72# Leap seconds are announced by the IERS in its Bulletin C. |
| 68# | 73# |
| 69# Leap seconds are announced by the IERS in its Bulletin C | 74# See www.iers.org for more details. |
| 70# | 75# |
| 71# See hpiers.obspm.fr or www.iers.org for more details. | 76# Every national laboratory and timing center uses the 77# data from the BIPM and the IERS to construct UTC(lab), 78# their local realization of UTC. |
| 72# | 79# |
| 73# All national laboratories and timing centers use the 74# data from the BIPM and the IERS to construct their 75# local realizations of UTC. 76# | |
| 77# Although the definition also includes the possibility | 80# Although the definition also includes the possibility |
| 78# of dropping seconds ("negative" leap seconds), this has 79# never been done and is unlikely to be necessary in the | 81# of dropping seconds ("negative" leap seconds), this has 82# never been done and is unlikely to be necessary in the |
| 80# foreseeable future. 81# 82# 5. If your system keeps time as the number of seconds since 83# some epoch (e.g., NTP timestamps), then the algorithm for 84# assigning a UTC time stamp to an event that happens during a positive | 83# foreseeable future. 84# 85# 5. If your system keeps time as the number of seconds since 86# some epoch (e.g., NTP timestamps), then the algorithm for 87# assigning a UTC time stamp to an event that happens during a positive |
| 85# leap second is not well defined. The official name of that leap 86# second is 23:59:60, but there is no way of representing that time 87# in these systems. 88# Many systems of this type effectively stop the system clock for 89# one second during the leap second and use a time that is equivalent 90# to 23:59:59 UTC twice. For these systems, the corresponding TAI | 88# leap second is not well defined. The official name of that leap 89# second is 23:59:60, but there is no way of representing that time 90# in these systems. 91# Many systems of this type effectively stop the system clock for 92# one second during the leap second and use a time that is equivalent 93# to 23:59:59 UTC twice. For these systems, the corresponding TAI |
| 91# timestamp would be obtained by advancing to the next entry in the 92# following table when the time equivalent to 23:59:59 UTC 93# is used for the second time. Thus the leap second which 94# occurred on 30 June 1972 at 23:59:59 UTC would have TAI 95# timestamps computed as follows: 96# 97# ... 98# 30 June 1972 23:59:59 (2287785599, first time): TAI= UTC + 10 seconds 99# 30 June 1972 23:59:60 (2287785599,second time): TAI= UTC + 11 seconds 100# 1 July 1972 00:00:00 (2287785600) TAI= UTC + 11 seconds 101# ... 102# 103# If your system realizes the leap second by repeating 00:00:00 UTC twice 104# (this is possible but not usual), then the advance to the next entry | 94# timestamp would be obtained by advancing to the next entry in the 95# following table when the time equivalent to 23:59:59 UTC 96# is used for the second time. Thus the leap second which 97# occurred on 30 June 1972 at 23:59:59 UTC would have TAI 98# timestamps computed as follows: 99# 100# ... 101# 30 June 1972 23:59:59 (2287785599, first time): TAI= UTC + 10 seconds 102# 30 June 1972 23:59:60 (2287785599,second time): TAI= UTC + 11 seconds 103# 1 July 1972 00:00:00 (2287785600) TAI= UTC + 11 seconds 104# ... 105# 106# If your system realizes the leap second by repeating 00:00:00 UTC twice 107# (this is possible but not usual), then the advance to the next entry |
| 105# in the table must occur the second time that a time equivlent to | 108# in the table must occur the second time that a time equivalent to |
| 106# 00:00:00 UTC is used. Thus, using the same example as above: 107# 108# ... 109# 30 June 1972 23:59:59 (2287785599): TAI= UTC + 10 seconds 110# 30 June 1972 23:59:60 (2287785600, first time): TAI= UTC + 10 seconds 111# 1 July 1972 00:00:00 (2287785600,second time): TAI= UTC + 11 seconds 112# ... 113# 114# in both cases the use of timestamps based on TAI produces a smooth | 109# 00:00:00 UTC is used. Thus, using the same example as above: 110# 111# ... 112# 30 June 1972 23:59:59 (2287785599): TAI= UTC + 10 seconds 113# 30 June 1972 23:59:60 (2287785600, first time): TAI= UTC + 10 seconds 114# 1 July 1972 00:00:00 (2287785600,second time): TAI= UTC + 11 seconds 115# ... 116# 117# in both cases the use of timestamps based on TAI produces a smooth |
| 115# time scale with no discontinuity in the time interval. | 118# time scale with no discontinuity in the time interval. However, 119# although the long-term behavior of the time scale is correct in both 120# methods, the second method is technically not correct because it adds 121# the extra second to the wrong day. |
| 116# | 122# |
| 117# This complexity would not be needed for negative leap seconds (if they 118# are ever used). The UTC time would skip 23:59:59 and advance from 119# 23:59:58 to 00:00:00 in that case. The TAI offset would decrease by 120# 1 second at the same instant. This is a much easier situation to deal 121# with, since the difficulty of unambiguously representing the epoch | 123# This complexity would not be needed for negative leap seconds (if they 124# are ever used). The UTC time would skip 23:59:59 and advance from 125# 23:59:58 to 00:00:00 in that case. The TAI offset would decrease by 126# 1 second at the same instant. This is a much easier situation to deal 127# with, since the difficulty of unambiguously representing the epoch |
| 122# during the leap second does not arise. 123# 124# Questions or comments to: 125# Judah Levine 126# Time and Frequency Division 127# NIST 128# Boulder, Colorado | 128# during the leap second does not arise. 129# 130# Questions or comments to: 131# Judah Levine 132# Time and Frequency Division 133# NIST 134# Boulder, Colorado |
| 129# jlevine@boulder.nist.gov | 135# Judah.Levine@nist.gov |
| 130# 131# Last Update of leap second values: 11 January 2012 132# | 136# 137# Last Update of leap second values: 11 January 2012 138# |
| 133# The following line shows this last update date in NTP timestamp | 139# The following line shows this last update date in NTP timestamp |
| 134# format. This is the date on which the most recent change to 135# the leap second data was added to the file. This line can | 140# format. This is the date on which the most recent change to 141# the leap second data was added to the file. This line can |
| 136# be identified by the unique pair of characters in the first two | 142# be identified by the unique pair of characters in the first two |
| 137# columns as shown below. 138# 139#$ 3535228800 140# 141# The NTP timestamps are in units of seconds since the NTP epoch, | 143# columns as shown below. 144# 145#$ 3535228800 146# 147# The NTP timestamps are in units of seconds since the NTP epoch, |
| 142# which is 1900.0. The Modified Julian Day number corresponding 143# to the NTP time stamp, X, can be computed as | 148# which is 1 January 1900, 00:00:00. The Modified Julian Day number 149# corresponding to the NTP time stamp, X, can be computed as |
| 144# 145# X/86400 + 15020 146# | 150# 151# X/86400 + 15020 152# |
| 147# where the first term converts seconds to days and the second 148# term adds the MJD corresponding to 1900.0. The integer portion 149# of the result is the integer MJD for that day, and any remainder 150# is the time of day, expressed as the fraction of the day since 0 151# hours UTC. The conversion from day fraction to seconds or to 152# hours, minutes, and seconds may involve rounding or truncation, 153# depending on the method used in the computation. | 153# where the first term converts seconds to days and the second 154# term adds the MJD corresponding to the time origin defined above. 155# The integer portion of the result is the integer MJD for that 156# day, and any remainder is the time of day, expressed as the 157# fraction of the day since 0 hours UTC. The conversion from day 158# fraction to seconds or to hours, minutes, and seconds may involve 159# rounding or truncation, depending on the method used in the 160# computation. |
| 154# | 161# |
| 155# The data in this file will be updated periodically as new leap | 162# The data in this file will be updated periodically as new leap |
| 156# seconds are announced. In addition to being entered on the line | 163# seconds are announced. In addition to being entered on the line |
| 157# above, the update time (in NTP format) will be added to the basic | 164# above, the update time (in NTP format) will be added to the basic |
| 158# file name leap-seconds to form the name leap-seconds.<NTP TIME>. | 165# file name leap-seconds to form the name leap-seconds.<NTP TIME>. |
| 159# In addition, the generic name leap-seconds.list will always point to | 166# In addition, the generic name leap-seconds.list will always point to |
| 160# the most recent version of the file. 161# 162# This update procedure will be performed only when a new leap second | 167# the most recent version of the file. 168# 169# This update procedure will be performed only when a new leap second |
| 163# is announced. | 170# is announced. |
| 164# 165# The following entry specifies the expiration date of the data | 171# 172# The following entry specifies the expiration date of the data |
| 166# in this file in units of seconds since 1900.0. This expiration date 167# will be changed at least twice per year whether or not a new leap 168# second is announced. These semi-annual changes will be made no 169# later than 1 June and 1 December of each year to indicate what 170# action (if any) is to be taken on 30 June and 31 December, | 173# in this file in units of seconds since the origin at the instant 174# 1 January 1900, 00:00:00. This expiration date will be changed 175# at least twice per year whether or not a new leap second is 176# announced. These semi-annual changes will be made no later 177# than 1 June and 1 December of each year to indicate what 178# action (if any) is to be taken on 30 June and 31 December, |
| 171# respectively. (These are the customary effective dates for new 172# leap seconds.) This expiration date will be identified by a 173# unique pair of characters in columns 1 and 2 as shown below. | 179# respectively. (These are the customary effective dates for new 180# leap seconds.) This expiration date will be identified by a 181# unique pair of characters in columns 1 and 2 as shown below. |
| 174# In the unlikely event that a leap second is announced with an | 182# In the unlikely event that a leap second is announced with an |
| 175# effective date other than 30 June or 31 December, then this 176# file will be edited to include that leap second as soon as it is 177# announced or at least one month before the effective date | 183# effective date other than 30 June or 31 December, then this 184# file will be edited to include that leap second as soon as it is 185# announced or at least one month before the effective date |
| 178# (whichever is later). 179# If an announcement by the IERS specifies that no leap second is 180# scheduled, then only the expiration date of the file will | 186# (whichever is later). 187# If an announcement by the IERS specifies that no leap second is 188# scheduled, then only the expiration date of the file will |
| 181# be advanced to show that the information in the file is still | 189# be advanced to show that the information in the file is still |
| 182# current -- the update time stamp, the data and the name of the file | 190# current -- the update time stamp, the data and the name of the file |
| 183# will not change. 184# | 191# will not change. 192# |
| 185# Updated through IERS Bulletin C46 186# File expires on: 28 June 2014 | 193# Updated through IERS Bulletin C48 194# File expires on: 28 June 2015 |
| 187# | 195# |
| 188#@ 3612902400 | 196#@ 3644438400 |
| 189# 1902272060800 10 # 1 Jan 1972 1912287785600 11 # 1 Jul 1972 1922303683200 12 # 1 Jan 1973 1932335219200 13 # 1 Jan 1974 1942366755200 14 # 1 Jan 1975 1952398291200 15 # 1 Jan 1976 1962429913600 16 # 1 Jan 1977 --- 20 unchanged lines hidden (view full) --- 217# the following special comment contains the 218# hash value of the data in this file computed 219# use the secure hash algorithm as specified 220# by FIPS 180-1. See the files in ~/pub/sha for 221# the details of how this hash value is 222# computed. Note that the hash computation 223# ignores comments and whitespace characters 224# in data lines. It includes the NTP values | 197# 1982272060800 10 # 1 Jan 1972 1992287785600 11 # 1 Jul 1972 2002303683200 12 # 1 Jan 1973 2012335219200 13 # 1 Jan 1974 2022366755200 14 # 1 Jan 1975 2032398291200 15 # 1 Jan 1976 2042429913600 16 # 1 Jan 1977 --- 20 unchanged lines hidden (view full) --- 225# the following special comment contains the 226# hash value of the data in this file computed 227# use the secure hash algorithm as specified 228# by FIPS 180-1. See the files in ~/pub/sha for 229# the details of how this hash value is 230# computed. Note that the hash computation 231# ignores comments and whitespace characters 232# in data lines. It includes the NTP values |
| 225# of both the last modification time and the | 233# of both the last modification time and the |
| 226# expiration time of the file, but not the 227# white space on those lines. 228# the hash line is also ignored in the 229# computation. 230# | 234# expiration time of the file, but not the 235# white space on those lines. 236# the hash line is also ignored in the 237# computation. 238# |
| 231#h 1151a8f e85a5069 9000fcdb 3d5e5365 1d505b37 | 239#h a4862ccd c6f43c6 964f3604 85944a26 b5cfad4e |