The Emirates Metrology Institute (EMI), the reference body for measurements in the UAE, has announced that a leap second will be added to UAE standard time just before 4am on July 1, when clocks will read 03:59:60.
The move aims to conform with other timing centres around the world, which will also add a leap second at the same time (11:59:60 pm UTC on June 30th) to adjust for the slight differences in time between highly accurate atomic clocks and the rotation of the globe.
Dr. Helal Al Kaabi, Executive Director of Emirates Metrology Institute, QCC, said, "EMI is closely monitoring all major metrological activities internationally to ensure active participation of the UAE in the development of metrology. Our latest move to add a leap second to UAE standard time follows a decision by the International Earth Rotation and Reference Systems Service, based at the Paris Observatory, in January 2015 to add a leap second to Coordinated Universal Time, UTC, at the end of June this year."
Until 1968, the length of the second was based on the rotation of the Earth by observing mean solar time at astronomical observatories. However, the rotation speed of the Earth fluctuates unpredictably, and has been found to even slow down due to friction caused by the ocean tides.
Today, more than 400 atomic clocks in around 70 institutes are combined to form the international time scale, called Coordinated Universal Time or UTC. These atomic clocks are significantly better at keeping time than the rotation of the Earth. The variations in the Earth's rotation cause the mean solar day to diverge gradually from the extremely stable UTC time scale. To prevent this difference from building up to more than 0.9 seconds, UTC is adjusted occasionally with a one-second step known as a 'leap second'.
Since the leap second procedure was introduced on 1st January 1972, a total of 25 leap seconds have been needed. The leap second at the end of June 2015 will be the 26th.
The Emirates Metrology Institute was launched by Abu Dhabi Quality and Conformity Council, to enable accurate measurements within manufacturing, research and environment sectors in the UAE. EMI's role is to maintain and disseminate the National reference standards, necessary to assure traceability of measurements, to international standards and the International System of Units, SI.