1 ### downloaded 2015-01-09 from ftp://time.nist.gov/pub/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.org 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 # Some systems implement leap seconds by amortizing the leap second
132 # over the last few minutes of the day. The frequency of the local
133 # clock is decreased (or increased) to realize the positive (or
134 # negative) leap second. This method removes the time step described
135 # above. Although the long-term behavior of the time scale is correct
136 # in this case, this method introduces an error during the adjustment
137 # period both in time and in frequency with respect to the official
140 # Questions or comments to:
142 # Time and Frequency Division
145 # Judah.Levine@nist.gov
147 # Last Update of leap second values: 5 January 2015
149 # The following line shows this last update date in NTP timestamp
150 # format. This is the date on which the most recent change to
151 # the leap second data was added to the file. This line can
152 # be identified by the unique pair of characters in the first two
153 # columns as shown below.
157 # The NTP timestamps are in units of seconds since the NTP epoch,
158 # which is 1 January 1900, 00:00:00. The Modified Julian Day number
159 # corresponding to the NTP time stamp, X, can be computed as
163 # where the first term converts seconds to days and the second
164 # term adds the MJD corresponding to the time origin defined above.
165 # The integer portion of the result is the integer MJD for that
166 # day, and any remainder is the time of day, expressed as the
167 # fraction of the day since 0 hours UTC. The conversion from day
168 # fraction to seconds or to hours, minutes, and seconds may involve
169 # rounding or truncation, depending on the method used in the
172 # The data in this file will be updated periodically as new leap
173 # seconds are announced. In addition to being entered on the line
174 # above, the update time (in NTP format) will be added to the basic
175 # file name leap-seconds to form the name leap-seconds.<NTP TIME>.
176 # In addition, the generic name leap-seconds.list will always point to
177 # the most recent version of the file.
179 # This update procedure will be performed only when a new leap second
182 # The following entry specifies the expiration date of the data
183 # in this file in units of seconds since the origin at the instant
184 # 1 January 1900, 00:00:00. This expiration date will be changed
185 # at least twice per year whether or not a new leap second is
186 # announced. These semi-annual changes will be made no later
187 # than 1 June and 1 December of each year to indicate what
188 # action (if any) is to be taken on 30 June and 31 December,
189 # respectively. (These are the customary effective dates for new
190 # leap seconds.) This expiration date will be identified by a
191 # unique pair of characters in columns 1 and 2 as shown below.
192 # In the unlikely event that a leap second is announced with an
193 # effective date other than 30 June or 31 December, then this
194 # file will be edited to include that leap second as soon as it is
195 # announced or at least one month before the effective date
196 # (whichever is later).
197 # If an announcement by the IERS specifies that no leap second is
198 # scheduled, then only the expiration date of the file will
199 # be advanced to show that the information in the file is still
200 # current -- the update time stamp, the data and the name of the file
203 # Updated through IERS Bulletin C49
204 # File expires on: 28 December 2015
208 2272060800 10 # 1 Jan 1972
209 2287785600 11 # 1 Jul 1972
210 2303683200 12 # 1 Jan 1973
211 2335219200 13 # 1 Jan 1974
212 2366755200 14 # 1 Jan 1975
213 2398291200 15 # 1 Jan 1976
214 2429913600 16 # 1 Jan 1977
215 2461449600 17 # 1 Jan 1978
216 2492985600 18 # 1 Jan 1979
217 2524521600 19 # 1 Jan 1980
218 2571782400 20 # 1 Jul 1981
219 2603318400 21 # 1 Jul 1982
220 2634854400 22 # 1 Jul 1983
221 2698012800 23 # 1 Jul 1985
222 2776982400 24 # 1 Jan 1988
223 2840140800 25 # 1 Jan 1990
224 2871676800 26 # 1 Jan 1991
225 2918937600 27 # 1 Jul 1992
226 2950473600 28 # 1 Jul 1993
227 2982009600 29 # 1 Jul 1994
228 3029443200 30 # 1 Jan 1996
229 3076704000 31 # 1 Jul 1997
230 3124137600 32 # 1 Jan 1999
231 3345062400 33 # 1 Jan 2006
232 3439756800 34 # 1 Jan 2009
233 3550089600 35 # 1 Jul 2012
234 3644697600 36 # 1 Jul 2015
236 # the following special comment contains the
237 # hash value of the data in this file computed
238 # use the secure hash algorithm as specified
239 # by FIPS 180-1. See the files in ~/pub/sha for
240 # the details of how this hash value is
241 # computed. Note that the hash computation
242 # ignores comments and whitespace characters
243 # in data lines. It includes the NTP values
244 # of both the last modification time and the
245 # expiration time of the file, but not the
246 # white space on those lines.
247 # the hash line is also ignored in the
250 #h 45e70fa7 a9df2033 f4a49ab0 ec648273 7b6c22c