diff options
Diffstat (limited to 'contrib/tzdata/leap-seconds.list')
| -rw-r--r-- | contrib/tzdata/leap-seconds.list | 158 |
1 files changed, 83 insertions, 75 deletions
diff --git a/contrib/tzdata/leap-seconds.list b/contrib/tzdata/leap-seconds.list index 7df3de6..0980e7b 100644 --- a/contrib/tzdata/leap-seconds.list +++ b/contrib/tzdata/leap-seconds.list @@ -1,10 +1,10 @@ # # In the following text, the symbol '#' introduces -# a comment, which continues from that symbol until +# a comment, which continues from that symbol until # the end of the line. A plain comment line has a # whitespace character following the comment indicator. -# There are also special comment lines defined below. -# A special comment will always have a non-whitespace +# There are also special comment lines defined below. +# A special comment will always have a non-whitespace # character in column 2. # # A blank line should be ignored. @@ -15,17 +15,22 @@ # are transmitted by almost all time services. # # The first column shows an epoch as a number of seconds -# since 1900.0 and the second column shows the number of -# seconds that must be added to UTC to compute TAI for -# any timestamp at or after that epoch. The value on -# each line is valid from the indicated initial instant -# until the epoch given on the next one or indefinitely -# into the future if there is no next line. +# since 1 January 1900, 00:00:00 (1900.0 is also used to +# indicate the same epoch.) Both of these time stamp formats +# ignore the complexities of the time scales that were +# used before the current definition of UTC at the start +# of 1972. (See note 3 below.) +# The second column shows the number of seconds that +# must be added to UTC to compute TAI for any timestamp +# at or after that epoch. The value on each line is +# valid from the indicated initial instant until the +# epoch given on the next one or indefinitely into the +# future if there is no next line. # (The comment on each line shows the representation of -# the corresponding initial epoch in the usual +# the corresponding initial epoch in the usual # day-month-year format. The epoch always begins at # 00:00:00 UTC on the indicated day. See Note 5 below.) -# +# # Important notes: # # 1. Coordinated Universal Time (UTC) is often referred to @@ -33,7 +38,7 @@ # longer used, and the use of GMT to designate UTC is # discouraged. # -# 2. The UTC time scale is realized by many national +# 2. The UTC time scale is realized by many national # laboratories and timing centers. Each laboratory # identifies its realization with its name: Thus # UTC(NIST), UTC(USNO), etc. The differences among @@ -44,10 +49,10 @@ # by the International Bureau of Weights and Measures # (BIPM). See www.bipm.fr for more information. # -# 3. The current defintion of the relationship between UTC -# and TAI dates from 1 January 1972. A number of different -# time scales were in use before than epoch, and it can be -# quite difficult to compute precise timestamps and time +# 3. The current definition of the relationship between UTC +# and TAI dates from 1 January 1972. A number of different +# time scales were in use before that epoch, and it can be +# quite difficult to compute precise timestamps and time # intervals in those "prehistoric" days. For more information, # consult: # @@ -58,36 +63,34 @@ # of Time," Proc. of the IEEE, Vol. 79, pp. 894-905, # July, 1991. # -# 4. The insertion of leap seconds into UTC is currently the -# responsibility of the International Earth Rotation Service, -# which is located at the Paris Observatory: -# -# Central Bureau of IERS -# 61, Avenue de l'Observatoire -# 75014 Paris, France. +# 4. The decision to insert a leap second into UTC is currently +# the responsibility of the International Earth Rotation and +# Reference Systems Service. (The name was changed from the +# International Earth Rotation Service, but the acronym IERS +# is still used.) # -# Leap seconds are announced by the IERS in its Bulletin C +# Leap seconds are announced by the IERS in its Bulletin C. # -# See hpiers.obspm.fr or www.iers.org for more details. +# See www.iers.org for more details. # -# All national laboratories and timing centers use the -# data from the BIPM and the IERS to construct their -# local realizations of UTC. +# Every national laboratory and timing center uses the +# data from the BIPM and the IERS to construct UTC(lab), +# their local realization of UTC. # # Although the definition also includes the possibility -# of dropping seconds ("negative" leap seconds), this has -# never been done and is unlikely to be necessary in the +# of dropping seconds ("negative" leap seconds), this has +# never been done and is unlikely to be necessary in the # foreseeable future. # # 5. If your system keeps time as the number of seconds since # some epoch (e.g., NTP timestamps), then the algorithm for # assigning a UTC time stamp to an event that happens during a positive -# leap second is not well defined. The official name of that leap -# second is 23:59:60, but there is no way of representing that time -# in these systems. -# Many systems of this type effectively stop the system clock for -# one second during the leap second and use a time that is equivalent -# to 23:59:59 UTC twice. For these systems, the corresponding TAI +# leap second is not well defined. The official name of that leap +# second is 23:59:60, but there is no way of representing that time +# in these systems. +# Many systems of this type effectively stop the system clock for +# one second during the leap second and use a time that is equivalent +# to 23:59:59 UTC twice. For these systems, the corresponding TAI # timestamp would be obtained by advancing to the next entry in the # following table when the time equivalent to 23:59:59 UTC # is used for the second time. Thus the leap second which @@ -102,7 +105,7 @@ # # If your system realizes the leap second by repeating 00:00:00 UTC twice # (this is possible but not usual), then the advance to the next entry -# in the table must occur the second time that a time equivlent to +# in the table must occur the second time that a time equivalent to # 00:00:00 UTC is used. Thus, using the same example as above: # # ... @@ -112,13 +115,16 @@ # ... # # in both cases the use of timestamps based on TAI produces a smooth -# time scale with no discontinuity in the time interval. -# -# This complexity would not be needed for negative leap seconds (if they -# are ever used). The UTC time would skip 23:59:59 and advance from -# 23:59:58 to 00:00:00 in that case. The TAI offset would decrease by -# 1 second at the same instant. This is a much easier situation to deal -# with, since the difficulty of unambiguously representing the epoch +# time scale with no discontinuity in the time interval. However, +# although the long-term behavior of the time scale is correct in both +# methods, the second method is technically not correct because it adds +# the extra second to the wrong day. +# +# This complexity would not be needed for negative leap seconds (if they +# are ever used). The UTC time would skip 23:59:59 and advance from +# 23:59:58 to 00:00:00 in that case. The TAI offset would decrease by +# 1 second at the same instant. This is a much easier situation to deal +# with, since the difficulty of unambiguously representing the epoch # during the leap second does not arise. # # Questions or comments to: @@ -126,66 +132,68 @@ # Time and Frequency Division # NIST # Boulder, Colorado -# jlevine@boulder.nist.gov +# Judah.Levine@nist.gov # # Last Update of leap second values: 11 January 2012 # -# The following line shows this last update date in NTP timestamp +# The following line shows this last update date in NTP timestamp # format. This is the date on which the most recent change to # the leap second data was added to the file. This line can -# be identified by the unique pair of characters in the first two +# be identified by the unique pair of characters in the first two # columns as shown below. # #$ 3535228800 # # The NTP timestamps are in units of seconds since the NTP epoch, -# which is 1900.0. The Modified Julian Day number corresponding -# to the NTP time stamp, X, can be computed as +# which is 1 January 1900, 00:00:00. The Modified Julian Day number +# corresponding to the NTP time stamp, X, can be computed as # # X/86400 + 15020 # -# where the first term converts seconds to days and the second -# term adds the MJD corresponding to 1900.0. The integer portion -# of the result is the integer MJD for that day, and any remainder -# is the time of day, expressed as the fraction of the day since 0 -# hours UTC. The conversion from day fraction to seconds or to -# hours, minutes, and seconds may involve rounding or truncation, -# depending on the method used in the computation. +# where the first term converts seconds to days and the second +# term adds the MJD corresponding to the time origin defined above. +# The integer portion of the result is the integer MJD for that +# day, and any remainder is the time of day, expressed as the +# fraction of the day since 0 hours UTC. The conversion from day +# fraction to seconds or to hours, minutes, and seconds may involve +# rounding or truncation, depending on the method used in the +# computation. # -# The data in this file will be updated periodically as new leap +# The data in this file will be updated periodically as new leap # seconds are announced. In addition to being entered on the line -# above, the update time (in NTP format) will be added to the basic +# above, the update time (in NTP format) will be added to the basic # file name leap-seconds to form the name leap-seconds.<NTP TIME>. -# In addition, the generic name leap-seconds.list will always point to +# In addition, the generic name leap-seconds.list will always point to # the most recent version of the file. # # This update procedure will be performed only when a new leap second -# is announced. +# is announced. # # The following entry specifies the expiration date of the data -# in this file in units of seconds since 1900.0. This expiration date -# will be changed at least twice per year whether or not a new leap -# second is announced. These semi-annual changes will be made no -# later than 1 June and 1 December of each year to indicate what -# action (if any) is to be taken on 30 June and 31 December, +# in this file in units of seconds since the origin at the instant +# 1 January 1900, 00:00:00. This expiration date will be changed +# at least twice per year whether or not a new leap second is +# announced. These semi-annual changes will be made no later +# than 1 June and 1 December of each year to indicate what +# action (if any) is to be taken on 30 June and 31 December, # respectively. (These are the customary effective dates for new # leap seconds.) This expiration date will be identified by a # unique pair of characters in columns 1 and 2 as shown below. -# In the unlikely event that a leap second is announced with an +# In the unlikely event that a leap second is announced with an # effective date other than 30 June or 31 December, then this # file will be edited to include that leap second as soon as it is # announced or at least one month before the effective date -# (whichever is later). -# If an announcement by the IERS specifies that no leap second is -# scheduled, then only the expiration date of the file will +# (whichever is later). +# If an announcement by the IERS specifies that no leap second is +# scheduled, then only the expiration date of the file will # be advanced to show that the information in the file is still -# current -- the update time stamp, the data and the name of the file +# current -- the update time stamp, the data and the name of the file # will not change. # -# Updated through IERS Bulletin C46 -# File expires on: 28 June 2014 +# Updated through IERS Bulletin C48 +# File expires on: 28 June 2015 # -#@ 3612902400 +#@ 3644438400 # 2272060800 10 # 1 Jan 1972 2287785600 11 # 1 Jul 1972 @@ -222,10 +230,10 @@ # computed. Note that the hash computation # ignores comments and whitespace characters # in data lines. It includes the NTP values -# of both the last modification time and the +# of both the last modification time and the # expiration time of the file, but not the # white space on those lines. # the hash line is also ignored in the # computation. # -#h 1151a8f e85a5069 9000fcdb 3d5e5365 1d505b37 +#h a4862ccd c6f43c6 964f3604 85944a26 b5cfad4e |
