World Metre Day is commemorated every year on May 20.
The Metre Convention on 20 May 1875 established the International Bureau of Weights and Measures (BIPM).
It provided the basis for a coherent measurement system worldwide.
The theme for World Metrology Day 2019 is “The International System of Units – Fundamentally better”.
This theme was chosen because in November 2018 as the General Conference on Weights and Measures agreed for “revisions” to the International System of Units (the SI Units) which was fixed in 1875.
The 7 base units of the SI system are
Currently, the way we measure four base units is redefined - kilogram, kelvin, mole and ampere.
Hereafter the SI units will be expressed in terms of the following constants.