1 ### downloaded 2014-12-20 from https://www.ietf.org/timezones/data/leap-seconds.list by weasel
3 # In the following text, the symbol '#' introduces
4 # a comment, which continues from that symbol until
5 # the end of the line. A plain comment line has a
6 # whitespace character following the comment indicator.
7 # There are also special comment lines defined below.
8 # A special comment will always have a non-whitespace
9 # character in column 2.
11 # A blank line should be ignored.
13 # The following table shows the corrections that must
14 # be applied to compute International Atomic Time (TAI)
15 # from the Coordinated Universal Time (UTC) values that
16 # are transmitted by almost all time services.
18 # The first column shows an epoch as a number of seconds
19 # since 1 January 1900, 00:00:00 (1900.0 is also used to
20 # indicate the same epoch.) Both of these time stamp formats
21 # ignore the complexities of the time scales that were
22 # used before the current definition of UTC at the start
23 # of 1972. (See note 3 below.)
24 # The second column shows the number of seconds that
25 # must be added to UTC to compute TAI for any timestamp
26 # at or after that epoch. The value on each line is
27 # valid from the indicated initial instant until the
28 # epoch given on the next one or indefinitely into the
29 # future if there is no next line.
30 # (The comment on each line shows the representation of
31 # the corresponding initial epoch in the usual
32 # day-month-year format. The epoch always begins at
33 # 00:00:00 UTC on the indicated day. See Note 5 below.)
37 # 1. Coordinated Universal Time (UTC) is often referred to
38 # as Greenwich Mean Time (GMT). The GMT time scale is no
39 # longer used, and the use of GMT to designate UTC is
42 # 2. The UTC time scale is realized by many national
43 # laboratories and timing centers. Each laboratory
44 # identifies its realization with its name: Thus
45 # UTC(NIST), UTC(USNO), etc. The differences among
46 # these different realizations are typically on the
47 # order of a few nanoseconds (i.e., 0.000 000 00x s)
48 # and can be ignored for many purposes. These differences
49 # are tabulated in Circular T, which is published monthly
50 # by the International Bureau of Weights and Measures
51 # (BIPM). See www.bipm.fr for more information.
53 # 3. The current definition of the relationship between UTC
54 # and TAI dates from 1 January 1972. A number of different
55 # time scales were in use before that epoch, and it can be
56 # quite difficult to compute precise timestamps and time
57 # intervals in those "prehistoric" days. For more information,
60 # The Explanatory Supplement to the Astronomical
63 # Terry Quinn, "The BIPM and the Accurate Measurement
64 # of Time," Proc. of the IEEE, Vol. 79, pp. 894-905,
67 # 4. The decision to insert a leap second into UTC is currently
68 # the responsibility of the International Earth Rotation and
69 # Reference Systems Service. (The name was changed from the
70 # International Earth Rotation Service, but the acronym IERS
73 # Leap seconds are announced by the IERS in its Bulletin C.
75 # See www.iers.org for more details.
77 # Every national laboratory and timing center uses the
78 # data from the BIPM and the IERS to construct UTC(lab),
79 # their local realization of UTC.
81 # Although the definition also includes the possibility
82 # of dropping seconds ("negative" leap seconds), this has
83 # never been done and is unlikely to be necessary in the
86 # 5. If your system keeps time as the number of seconds since
87 # some epoch (e.g., NTP timestamps), then the algorithm for
88 # assigning a UTC time stamp to an event that happens during a positive
89 # leap second is not well defined. The official name of that leap
90 # second is 23:59:60, but there is no way of representing that time
92 # Many systems of this type effectively stop the system clock for
93 # one second during the leap second and use a time that is equivalent
94 # to 23:59:59 UTC twice. For these systems, the corresponding TAI
95 # timestamp would be obtained by advancing to the next entry in the
96 # following table when the time equivalent to 23:59:59 UTC
97 # is used for the second time. Thus the leap second which
98 # occurred on 30 June 1972 at 23:59:59 UTC would have TAI
99 # timestamps computed as follows:
102 # 30 June 1972 23:59:59 (2287785599, first time): TAI= UTC + 10 seconds
103 # 30 June 1972 23:59:60 (2287785599,second time): TAI= UTC + 11 seconds
104 # 1 July 1972 00:00:00 (2287785600) TAI= UTC + 11 seconds
107 # If your system realizes the leap second by repeating 00:00:00 UTC twice
108 # (this is possible but not usual), then the advance to the next entry
109 # in the table must occur the second time that a time equivalent to
110 # 00:00:00 UTC is used. Thus, using the same example as above:
113 # 30 June 1972 23:59:59 (2287785599): TAI= UTC + 10 seconds
114 # 30 June 1972 23:59:60 (2287785600, first time): TAI= UTC + 10 seconds
115 # 1 July 1972 00:00:00 (2287785600,second time): TAI= UTC + 11 seconds
118 # in both cases the use of timestamps based on TAI produces a smooth
119 # time scale with no discontinuity in the time interval. However,
120 # although the long-term behavior of the time scale is correct in both
121 # methods, the second method is technically not correct because it adds
122 # the extra second to the wrong day.
124 # This complexity would not be needed for negative leap seconds (if they
125 # are ever used). The UTC time would skip 23:59:59 and advance from
126 # 23:59:58 to 00:00:00 in that case. The TAI offset would decrease by
127 # 1 second at the same instant. This is a much easier situation to deal
128 # with, since the difficulty of unambiguously representing the epoch
129 # during the leap second does not arise.
131 # Questions or comments to:
133 # Time and Frequency Division
136 # Judah.Levine@nist.gov
138 # Last Update of leap second values: 11 January 2012
140 # The following line shows this last update date in NTP timestamp
141 # format. This is the date on which the most recent change to
142 # the leap second data was added to the file. This line can
143 # be identified by the unique pair of characters in the first two
144 # columns as shown below.
148 # The NTP timestamps are in units of seconds since the NTP epoch,
149 # which is 1 January 1900, 00:00:00. The Modified Julian Day number
150 # corresponding to the NTP time stamp, X, can be computed as
154 # where the first term converts seconds to days and the second
155 # term adds the MJD corresponding to the time origin defined above.
156 # The integer portion of the result is the integer MJD for that
157 # day, and any remainder is the time of day, expressed as the
158 # fraction of the day since 0 hours UTC. The conversion from day
159 # fraction to seconds or to hours, minutes, and seconds may involve
160 # rounding or truncation, depending on the method used in the
163 # The data in this file will be updated periodically as new leap
164 # seconds are announced. In addition to being entered on the line
165 # above, the update time (in NTP format) will be added to the basic
166 # file name leap-seconds to form the name leap-seconds.<NTP TIME>.
167 # In addition, the generic name leap-seconds.list will always point to
168 # the most recent version of the file.
170 # This update procedure will be performed only when a new leap second
173 # The following entry specifies the expiration date of the data
174 # in this file in units of seconds since the origin at the instant
175 # 1 January 1900, 00:00:00. This expiration date will be changed
176 # at least twice per year whether or not a new leap second is
177 # announced. These semi-annual changes will be made no later
178 # than 1 June and 1 December of each year to indicate what
179 # action (if any) is to be taken on 30 June and 31 December,
180 # respectively. (These are the customary effective dates for new
181 # leap seconds.) This expiration date will be identified by a
182 # unique pair of characters in columns 1 and 2 as shown below.
183 # In the unlikely event that a leap second is announced with an
184 # effective date other than 30 June or 31 December, then this
185 # file will be edited to include that leap second as soon as it is
186 # announced or at least one month before the effective date
187 # (whichever is later).
188 # If an announcement by the IERS specifies that no leap second is
189 # scheduled, then only the expiration date of the file will
190 # be advanced to show that the information in the file is still
191 # current -- the update time stamp, the data and the name of the file
194 # Updated through IERS Bulletin C48
195 # File expires on: 28 June 2015
199 2272060800 10 # 1 Jan 1972
200 2287785600 11 # 1 Jul 1972
201 2303683200 12 # 1 Jan 1973
202 2335219200 13 # 1 Jan 1974
203 2366755200 14 # 1 Jan 1975
204 2398291200 15 # 1 Jan 1976
205 2429913600 16 # 1 Jan 1977
206 2461449600 17 # 1 Jan 1978
207 2492985600 18 # 1 Jan 1979
208 2524521600 19 # 1 Jan 1980
209 2571782400 20 # 1 Jul 1981
210 2603318400 21 # 1 Jul 1982
211 2634854400 22 # 1 Jul 1983
212 2698012800 23 # 1 Jul 1985
213 2776982400 24 # 1 Jan 1988
214 2840140800 25 # 1 Jan 1990
215 2871676800 26 # 1 Jan 1991
216 2918937600 27 # 1 Jul 1992
217 2950473600 28 # 1 Jul 1993
218 2982009600 29 # 1 Jul 1994
219 3029443200 30 # 1 Jan 1996
220 3076704000 31 # 1 Jul 1997
221 3124137600 32 # 1 Jan 1999
222 3345062400 33 # 1 Jan 2006
223 3439756800 34 # 1 Jan 2009
224 3550089600 35 # 1 Jul 2012
226 # the following special comment contains the
227 # hash value of the data in this file computed
228 # use the secure hash algorithm as specified
229 # by FIPS 180-1. See the files in ~/pub/sha for
230 # the details of how this hash value is
231 # computed. Note that the hash computation
232 # ignores comments and whitespace characters
233 # in data lines. It includes the NTP values
234 # of both the last modification time and the
235 # expiration time of the file, but not the
236 # white space on those lines.
237 # the hash line is also ignored in the
240 #h a4862ccd c6f43c6 964f3604 85944a26 b5cfad4e