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UTC
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... Version-3 local-clock algorithms to
avoid problems observed when leap seconds are introduced in the UTC
timescale and also to support an auxiliary precision oscillator, such as
a cesium clock or timing receiver ...
... (NTP) timescale relative to the
Coordinated Universal Time (UTC) timescale, and establishes the precise
interpretation of UTC leap seconds in NTP ...
... Coordinated Universal Time (UTC) timescale, and establishes the precise
interpretation of UTC leap seconds in NTP.
...
... network to run at the same frequency, to
synchronize time means to set the clocks so that all agree at a
particular epoch with respect to UTC, as provided by international
standards, and to synchronize clocks means to synchronize them in both
frequency and time.
...
... relative to the standard oscillator. Another goal of this presentation
is to describe a standard chronometry to rationalize conventional
computer time and UTC; in particular, how to handle leap seconds.
...
... bps using a 100-Hz subcarrier on the broadcast signal.
The timecode information includes UTC time-day information, but does not
currently include year or leap-second warning. While these transmissions
and those of Canada from Ottawa, Ontario (CHU), and other countries can
...
... kHz from Rugby, U.K. (MSF), and on 77.5 kHz from Mainflingen, West
Germany (DCF77). The timecode information includes UTC time-day-year
information and leap-second warning. Radio clocks which operate with
these transmissions include the Spectracom 8170 and Kinemetrics/TrueTime
...
... 4-bit binary-coded decimal
words transmitted over an interval of 30 seconds. The timecode
information includes UTC time-day-year information and leap-second
warning. Radio clocks which operate with these transmissions include the
Kinemetrics/TrueTime 468-DC ...
... nanoseconds [VAN84]. The timecode information includes GPS time and UTC
correction; however, there appears to be no leap-second warning. Radio
clocks which operate with these transmissions include the
...
... ground wave area, there is no timecode modulation, so the receiver must
be supplied with UTC time to within a few tens of seconds from an
external source before operation begins.
...
... timecode modulation, so the receiver must be supplied with geographic
coordinates within a degree and UTC time within five seconds from an
external source before operation begins. There are several other VLF
services intended primarily for worldwide data communications with
...
... The International Bureau of Weights and Measures (IBWM) uses
astronomical observations provided by the U.S. Naval Observatory and
other observatories to determine UTC. Starting from apparent mean solar
time as observed, the UT0 timescale is determined using corrections for
...
...
For the most precise coordination and timestamping of events since 1972,
it is necessary to know when leap seconds are implemented in UTC and how
the seconds are numbered. As specified in CCIR Report 517, which is
reproduced in [BLA74 ...
... Note that the NTP time column actually shows the epoch following the
last second of the day given in the UTC date and MJD columns (except for
the first line), which is the precise epoch of insertion. The offset
column shows the cumulative seconds offset between the uncoordinated
...
... the first line), which is the precise epoch of insertion. The offset
column shows the cumulative seconds offset between the uncoordinated
(Julian) timescale and the UTC timescale; that is, the number of seconds
to add to the Julian clock in order to maintain nominal agreement with
...
... to add to the Julian clock in order to maintain nominal agreement with
the UTC clock. Finally, note that the epoch of insertion is relative to
the timescale immediately prior to that epoch; e.g., the epoch of the 31
December 90 insertion is determined on the timescale in effect following
...
... the 31 December 1990 insertion, which means the actual insertion
relative to the Julian clock is fourteen seconds later than the apparent
time on the UTC timescale.
...
...
The UTC timescale thus ticks in standard (atomic) seconds and was set to
the value 0h MJD 41,317.0 at the epoch determined by astronomical
observation to be 0h on 1 January 1972 according to the Gregorian
...
... the value 0h MJD 41,317.0 at the epoch determined by astronomical
observation to be 0h on 1 January 1972 according to the Gregorian
calendar; that is, the inaugural tick of the UTC Era. In fact, the
inaugural tick which synchronized the cosmic oscillators, Julian clock,
UTC clock and Gregorian ...
... ; that is, the inaugural tick of the UTC Era. In fact, the
inaugural tick which synchronized the cosmic oscillators, Julian clock,
UTC clock and Gregorian calendar forevermore was displaced about ten
seconds from the civil clock then in use, while the GPS ...
... seconds from the civil clock then in use, while the GPS clock is ahead
of the UTC clock by six seconds in late 1990. Subsequently, the UTC
clock has marched backward relative to the Julian timescale exactly one
...
... GPS clock is ahead
of the UTC clock by six seconds in late 1990. Subsequently, the UTC
clock has marched backward relative to the Julian timescale exactly one
second on scheduled occasions at monumental epoches embedded in the
...
... second adjustments affect the number of seconds per day and thus the
number of seconds per year. Apparently, should we choose to worry about
it, the UTC clock, Julian clock and various cosmic clocks will
inexorably drift apart with time until rationalized by some future papal
bull.
...
...
The NTP timescale is based on the UTC timescale, but not necessarily
always coincident with it. At 0h on 1 January 1972 (MJD 41,317.0), the
first tick of the UTC ...
... UTC timescale, but not necessarily
always coincident with it. At 0h on 1 January 1972 (MJD 41,317.0), the
first tick of the UTC Era, the NTP clock was set to 2,272,060,800,
representing the number of standard seconds since 0h on 1 January 1900
...
... NTP clock was set to 2,272,060,800,
representing the number of standard seconds since 0h on 1 January 1900
(MJD 15,020.0). The insertion of leap seconds in UTC and subsequently
into NTP does not affect the UTC ...
... UTC and subsequently
into NTP does not affect the UTC or NTP oscillator, only the conversion
to conventional civil UTC time ...
... UTC or NTP oscillator, only the conversion
to conventional civil UTC time. However, since the only institutional
memory available to NTP are the UTC ...
... UTC time. However, since the only institutional
memory available to NTP are the UTC timecode broadcast services, the NTP ...
... services, the NTP
timescale is in effect reset to UTC as each timecode is received. Thus,
when a leap second is inserted in UTC and subsequently in NTP ...
... timescale is in effect reset to UTC as each timecode is received. Thus,
when a leap second is inserted in UTC and subsequently in NTP, knowledge
of all previous leap seconds is lost.
...
... mention the apparent origin of the timescale itself, lurch backward one
second as each new timescale is established. If a clock synchronized to
NTP in 1990 was used to establish the UTC epoch of an event that
occurred in early 1972 without correction, the event would appear
fifteen seconds late relative to UTC ...
... UTC epoch of an event that
occurred in early 1972 without correction, the event would appear
fifteen seconds late relative to UTC. However, NTP primary time servers
...
... set to the broadcast value on the current timescale. As a result, for
the most precise determination of epoch relative to the historic UTC
clock, the user must subtract from the apparent NTP epoch the offsets
...
... day one second longer than usual, the NTP day rollover will not occur
until the end of the first occurrence of second 800. The UTC time
conversion routines must notice the apparent time and the leap bits and
...
... handle the timescale conversions accordingly. Immediately after the leap
insertion both timescales resume ticking the seconds as if the leap had
never happened. The chronometric correspondence between the UTC and NTP
timescales continues, but NTP ...
... NTP has forgotten about all past leap
insertions. In NTP chronometric determination of UTC time intervals
spanning leap seconds will thus be in error, unless the exact times of
insertion are known.
...