If all goes correctly she will see the clock read 11:59:59 pm, then 11:59:60 pm, then 12:00:00 am, that is she will see the insertion of a leap second
. (20) These seconds are added into UTC in order for it to keep roughly in line with both TAI and UT1.
The last leap second
was witnessed in 2012 but as predicted, widespread problems across the globe came to the fore.
At 23.59 Greenwich Mean Time (GMT) on June 30, the earth will experience a minute that will last 61 seconds -- the extra second is called the leap second
Several such slowdowns have been juggled in -- in fact from the 1970s, when leap seconds
were found necessary, 25 such have already been added in, most recently being in 2012.
The International Earth Rotation and Reference Systems Service said the leap second
was added to account for the small difference in time between the rotation of the globe and the atomic clocks, reports (https://au.news.yahoo.com/technology/a/25910271/leap-second-to-make-june-30-2015-a-longer-day-paris-observatory-announces/) Yahoo News .
In some cases it appears that some techies only guessed that the problem was related to the leap second
because it happened to occur precisely at the moment of midnight UTC/GMT.
The matter of a simple leap second
also cost travellers hours and left passengers stranded all across the country.
Among specific topics are leap seconds
in literature, time scales in astronomical and navigational almanacs, telescope systems at Lick Observatory and Keck Observatory, and automating retrieval of Earth orientation predictions.
As a leap year, and with two additional leap seconds
added, it was the longest year ever.
Users never need to set the clock as it automatically adjusts for daylight saving, leap year, and even the earth's wobble in leap seconds
. The clock maintains better than 1-sec accuracy for 25,000 years, and radio signal from NIST's Colorado atomic clock automatically sets the correct time/date.
In order for our civil time (UTC based on TAI) to keep "in step" with the changing earth rotational speed, UT1 leap seconds
are added to the year from time to time to compensate for this slowing down.
Confusion sometimes arises over the misconception that the regular insertion of leap seconds
every few years indicates that the Earth should stop rotating within a few millennia.
Timekeepers argue that both measures are useful but haven't agreed when to add leap seconds
to make the planetary and the atomic clock years match up (SN: 4/22/06, p.
It's not as if professional astronomers couldn't make the necessary corrections, Seaman adds, but abandoning leap seconds
would be a complicated and expensive proposition.
were introduced in 1972, but this is the first to be used for seven years.