1#
2# In the following text, the symbol '#' introduces
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.
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
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.
29# (The comment on each line shows the representation of
30# the corresponding initial epoch in the usual
31# day-month-year format. The epoch always begins at
32# 00:00:00 UTC on the indicated day. See Note 5 below.)
33#
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#
41# 2. The UTC time scale is realized by many national
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#
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
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#
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.)
71#
72# Leap seconds are announced by the IERS in its Bulletin C.
73#
74# See www.iers.org for more details.
75#
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.
79#
80# Although the definition also includes the possibility
81# of dropping seconds ("negative" leap seconds), this has
82# never been done and is unlikely to be necessary in the
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
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
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
108# in the table must occur the second time that a time equivalent to
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
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.
122#
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
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
135# Judah.Levine@nist.gov
136#
137# Last Update of leap second values: 11 January 2012
138#
139# The following line shows this last update date in NTP timestamp
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
142# be identified by the unique pair of characters in the first two
143# columns as shown below.
144#
145#$ 3535228800
146#
147# The NTP timestamps are in units of seconds since the NTP epoch,
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
150#
151# X/86400 + 15020
152#
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.
161#
162# The data in this file will be updated periodically as new leap
163# seconds are announced. In addition to being entered on the line
164# above, the update time (in NTP format) will be added to the basic
165# file name leap-seconds to form the name leap-seconds.<NTP TIME>.
166# In addition, the generic name leap-seconds.list will always point to
167# the most recent version of the file.
168#
169# This update procedure will be performed only when a new leap second
170# is announced.
171#
172# The following entry specifies the expiration date of the data
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,
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.
182# In the unlikely event that a leap second is announced with an
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
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
189# be advanced to show that the information in the file is still
190# current -- the update time stamp, the data and the name of the file
191# will not change.
192#
193# Updated through IERS Bulletin C48
194# File expires on: 28 June 2015
195#
196#@ 3644438400
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
233# of both the last modification time and the
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#
239#h a4862ccd c6f43c6 964f3604 85944a26 b5cfad4e
2# In the following text, the symbol '#' introduces
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.
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
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.
29# (The comment on each line shows the representation of
30# the corresponding initial epoch in the usual
31# day-month-year format. The epoch always begins at
32# 00:00:00 UTC on the indicated day. See Note 5 below.)
33#
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#
41# 2. The UTC time scale is realized by many national
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#
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
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#
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.)
71#
72# Leap seconds are announced by the IERS in its Bulletin C.
73#
74# See www.iers.org for more details.
75#
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.
79#
80# Although the definition also includes the possibility
81# of dropping seconds ("negative" leap seconds), this has
82# never been done and is unlikely to be necessary in the
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
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
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
108# in the table must occur the second time that a time equivalent to
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
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.
122#
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
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
135# Judah.Levine@nist.gov
136#
137# Last Update of leap second values: 11 January 2012
138#
139# The following line shows this last update date in NTP timestamp
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
142# be identified by the unique pair of characters in the first two
143# columns as shown below.
144#
145#$ 3535228800
146#
147# The NTP timestamps are in units of seconds since the NTP epoch,
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
150#
151# X/86400 + 15020
152#
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.
161#
162# The data in this file will be updated periodically as new leap
163# seconds are announced. In addition to being entered on the line
164# above, the update time (in NTP format) will be added to the basic
165# file name leap-seconds to form the name leap-seconds.<NTP TIME>.
166# In addition, the generic name leap-seconds.list will always point to
167# the most recent version of the file.
168#
169# This update procedure will be performed only when a new leap second
170# is announced.
171#
172# The following entry specifies the expiration date of the data
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,
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.
182# In the unlikely event that a leap second is announced with an
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
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
189# be advanced to show that the information in the file is still
190# current -- the update time stamp, the data and the name of the file
191# will not change.
192#
193# Updated through IERS Bulletin C48
194# File expires on: 28 June 2015
195#
196#@ 3644438400
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
233# of both the last modification time and the
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#
239#h a4862ccd c6f43c6 964f3604 85944a26 b5cfad4e