Time Systems and Dates - GPS Time
A leap second is a one-second adjustment that is occasionally applied to civil time Coordinated On clocks that display local time tied to UTC, the leap second may be inserted . If the difference between solar time at a particular location and local time . It is also easy to convert GPS time to TAI, as TAI is always exactly Our GPS-synchronized products precisely adjust for leap seconds to keep them When the difference between UTC and apparent Earth time has exceeded a. Coordinated Universal Time (UTC), an atomic time, is the basis for civil time. the relationship between the frequency of the cesium atom (the standard of time) and the ephemeris second. . UTC. GPS Time is NOT adjusted for leap seconds.
Greenwich is the historical reference not only for longitude Greenwich meridian but also for Universal Time UT1 based on the Earth rotation.
While the TAI and UT1 time scales are precisely defined, the former by atomic clocks and the latter by astronomical observations, UTC is a compromise, stepping with atomic seconds and periodically reset by a leap second to the astronomical time of Greenwich; the intention is to keep civil time aligned with UT1. However, even at Greenwich, leap seconds do not ensure that the sun culminates exactly at All sundials show an offset to civil time.
Orienting a space telescope such as the Hubble Space Telescope cannot use leap seconds. If the difference between solar time at a particular location and local time would matter, users simply need to know the difference of UTC to UT1, DUT1 which is broadcastas they need to know the difference of their location to the Greenwich meridian their longitude.
Citizens accept yearly variations of one hour because of daylight saving timethey do not care about second-accurate noon. In Europe, citizens are split whether to adopt permanently summer time or standard time, they do not care about leap seconds. If the difference between solar noon and local time The irregularity and unpredictability of UTC leap seconds is problematic for several areas, especially computing.
For example, to compute the elapsed time in seconds between two given UTC past dates requires the consultation of a table of leap seconds, which needs to be updated whenever a new leap second is announced. Moreover, it is not possible to compute accurate time intervals for UTC dates that are more than about six months in the future.
Standard of time definition: UTC, GPS, LORAN and TAI
With increasing requirements for accuracy in automation systems and high-speed trading, this raises a number of issues, as a leap second represents a jump often a million times larger than the required accuracy for industry clocks. A number of objections to the proposal have been raised. Kenneth Seidelmann, editor of the Explanatory Supplement to the Astronomical Almanac, wrote a letter lamenting the lack of consistent public information about the proposal and adequate justification.
Demetrios Matsakis, the United States Naval Observatory 's Chief Scientist for Time Services, presented the reasoning in favor of the redefinition and rebuttals to the arguments made against it.
The possibility of leap seconds being a hazard to navigation was presented, as well as the observed effects on commerce. The United States formulated its position on this matter based upon the advice of the National Telecommunications and Information Administration  and the Federal Communications Commission FCCwhich solicited comments from the general public.
The vote was ultimately deferred. Han expressed his personal view in favor of abolishing the leap second,  and similar support for the redefinition was again expressed by Dr. At a special session of the Asia-Pacific Telecommunity Meeting on February 10,Chunhao Han indicated China was now supporting the elimination of future leap seconds, as were all the other presenting national representatives from Australia, Japan, and the Republic of Korea.
Computers, for example, could use these and convert to UTC or local civil time as necessary for output. Systems that cannot tolerate disruptions caused by leap seconds can base their time on TAI and use Precision Time Protocol. However, the BIPM has pointed out that this proliferation of timescales leads to confusion.
Time Scales: UT1, UTC, TAI, ET, TT, GPS time
The plan for the vote was: The ITU-R released its status paper, Status of Coordinated Universal Time UTC study in ITU-R, in preparation for the January meeting in Geneva; the paper reported that, to date, in response to the UN agency's and web based surveys requesting input on the topic, it had received 16 responses from the Member States with "13 being in favor of change, 3 being contrary. The ITU makes a decision. In Januaryrather than decide yes or no per this plan, the ITU decided to postpone a decision on leap seconds to the World Radiocommunication Conference in November At this conference, it was again decided to continue using leap seconds, pending further study and consideration at the next conference in Felicitas Arias, who, as Director of the International Bureau of Weights and Measures BIPM 's Time, Frequency, and Gravimetry Department, is responsible for generating UTC, noted in a press release that the drift of about one minute every 60—90 years could be compared to the minute annual variation between true solar time and mean solar time, the one hour offset by use of daylight time, and the several-hours offset in certain geographically extra-large time zones.
This counter has no indicator that a leap second is occurring. Some computers, in particular Linux, assign to the leap second the number of the preceding Since there is no standard governing the sequence, the time stamp values can vary by one second.
The days of the week are numbered, with Sunday being 0, 1 Monday, etc.
Within each week the time is usually denoted as the second of the week. This is a number between 0 and60 x 60 x 24x 7. The word "uniformly" is used above to indicate that there are no "leap seconds" in this time system. The world does not rotate smoothly. This can easily be measured with atomic clocks.
A plot of the difference between atomic clock time and "earth" time shows a slow drift with some small irregularities. Below is a plot of the difference between earth rotation time UT1 and the atomic time used by science - UTC. The jumps are where UTC was adjusted to keep it within a second of earth rotation time. Leap Seconds were introduced there. The current slow drift is not constant over decades and comes back.
The source of these variations are many, some unknown. Tidal effects can be predicted over centuries, but there have been changes due to things like the 's el Nino event and even large geomagnetic storms.02 Webinar II -- GPS & IMU - GPS Time to UTC Epoch Time
A data set available at the IERS goes back to It is based on an analysis of astronomical events and historic data.