The Guyana National Bureau of Standards (GNBS) has announced that it would adopt several changes to the International System of Units that will come into effect on May 20, 2019. The announcement came in light of Sunday having been World Metrology Day observance of which was under the theme: Constant evolution of the International System of UnitsAccording to a release, GNBS will continue to promote metric system units even as the Global Measurement Systems continue to undergo revision. It was announced that some of the changes are being modified to accommodate future improvements in the technologies used to realise them.The second, the metre, the kilogram, the ampere, the kelvin, the mole and the candela (the base units), are being revised to update the definitions of four of these units.GNBS disclosed that come November 2018, revised definitions of the kilogram, ampere, kelvin and mole are expected to be approved by the General Conference on Weights and Measures (CGPM).“The revised definitions will be based on seven physical constants (for example, the speed of light, the Planck constant and the Avogadro constant) and are therefore inherently stable,” the release identified.The public is being informed that the value of the Planck constant will be chosen to ensure that there will be no change in the SI kilogram at the time of redefinition, while the ampere and other electrical units will become fully consistent with the definitions of those units. It was also explained that the kelvin measurement will be redefined with no immediate effect on temperature measurement practice, or on the traceability of temperature measurements; and for most users, it will pass unnoticed.The release observed that the mole will be redefined with respect to a specified number of entities, and will no longer depend on the unit of mass, the kilogram; while the metre will continue to be defined in terms of the speed of light, one of the fundamental constants of physics.According to GNBS, the candela will continue to be defined in terms of Kcd, which is a technical constant for photometry, and will therefore continue to be linked to the watt.GNBS gave all assurances that “care has been taken to ensure that there will be no perceptible impact on daily life, and that measurements made with previous definitions of the units remain valid within their measurement uncertainties”.“Few users outside national metrology laboratories will notice the changes. Reaching the experimental accuracies and fulfilling the conditions requested in the CGPM resolutions has been a remarkable accomplishment, which will ensure that the SI continues to meet the needs of even the most demanding users,” the state body added.