30 June 2015 clocked one second longer with a leap second added to clocks worldwide

Jul 1, 2015 10:00 IST

clocks world-wide30 June2015 clocked one second longer as an extra second or a leap second was added to clocks world- wide after 23:59:59.

With the addition of 61st second to the 59th minute of the 23rd hour, clocks across the world registered 23:59:60 before turning on to 00:00:00 on 1 July 2015.

In India, the leap second was added by scientists at the Time and Frequency Standards Laboratory (TFSL) to atomic clocks after 05:29:59 as the Indian Standard Time (IST) is ahead of the Coordinated Universal Time (UTC) by 5 and half hours. UTC is the advanced version of Greenwich Mean Time (GMT).

TFSL is the nation’s official time keeper and located at the National Physical Laboratory (NPL) in New Delhi.

The decision to add a leap second was taken by the International Earth Rotation and Reference Systems Service (IERS), the global official time keeper, in December 2014 in order to synchronise the Coordinated Universal Time (UTC) with the Universal Time (UT).

Difference between UTC and UT

Though the two systems are meant to measure time to the accurate level possible, there is a primary difference between them with respect to their respective reference points.

While the UTC, the basis for civil time across the world, relies on atomic clocks for its sustenance as overseen by the International Telecommunication Union (ITU), the UT is based on time taken by the Earth to complete rotations around itself with respect to the Sun as observed by worldwide network of stations by employing Very Long Baseline Interferometry (VLBI) technique.

Why the difference?

Usually, any lag between the two time systems occurs due to regular fluctuations in the earth’s rotation speeds as atomic clocks are foolproof and can only go wrong once in 30 million years that too for nano seconds.

The Earth is a floating object in the space and its pace is disturbed by geological events such as volcanic eruptions and earthquakes and interplay of gravitational forces among the Sun, the Earth and the Moon.

All these internal and external forces have an impact on the mass of the Earth and ultimately the time taken by it to complete the rotation. For example, glacial rebound shortens the solar day by 0.6 ms/century and the 2004 Indian Ocean earthquake is thought to have shortened it by 2.68 microseconds.

Usually, a positive leap second (PLS) is added to clocks when the earth takes more than 86400 seconds to complete one rotation and a negative leap second (NLS) is added when it moves faster in the space.

The practice of adding a PLS

So far, only PLS was put into practice and the Leap Second 2015 is the 26th in the series since the system of leap second was introduced in 1972. The previous leap second was added on 30 June 2012.

The concept of leap second is similar to leap year and Daylight Saving Time (DST) mechanisms that are in practice to ensure our clocks show the right time and free us from a future hypothetical situation where in, we go to bed while our wrist watch is showing 9 am.

Usually, a leap second is added on 30 June or 31 December to give effect to the notifications issued by the IERS prior to six months of its inclusion.

In accordance with the IERS’s notification, atomic clocks are tinkered with by the International Bureau of Weights and Measures (BIPM) that are maintained worldwide.

Though the concept of leap second has been appreciated for its utility in showing the time right, it has attracted severe criticism in recent times from business quarters and
military personnel.

Firms contend that frequent ad-hoc changes to international time systems will result in harm to time-sensitive systems like computer programmes and trading platforms that are at the core of the modern economy. The disturbance to the businesses was evident from crashing of IT and airline services when a leap second was introduced in 2012.

Though disturbances to businesses were not reported during the leap second 2015; In view of the lingering opposition to the continuation of the sytem from its member countries, the ITU will be holding the World Radiocommunication Conference in Switzerland in November 2015 to decide its fate.

India is officially is in favour of redefining the leap second system along with the USA, Japan and France.

How India handles its clocks?

India observes a unified timing system call as Indian Standard Time (IST) with a time offset of UTC+05:30.

It is calculated on the basis of 82.5° E longitude, in Shankargarh Fort, Mirzapur (25.15°N 82.58°E) in Allahabad district in the state of Uttar Pradesh.

In recent times, there have been proposals from different quarters to divide the country into different time zones as the country's east–west distance is nearly 2933 kms.

The distance covers over 28 degrees of longitude or 112 minutes resulting in the sun rising and setting almost two hours earlier on India's eastern border than in the Rann of Kutch in the far west as a result of which inhabitants of the northeastern states have to advance their clocks with the early sunrise and avoid the extra consumption of energy after daylight hours

A four member committee under the Ministry of Science and Technology to examine the need for multiple time zones and daylight saving submitted its report in 2004 to the Parliament.

The committee did not recommend changes to the unified time system in the country as the prime meridian was chosen with reference to a central station and that the expanse of the Indian State was not large.

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