Commonwealth Day is an annual observance held on the second Monday in March.
Each member of the Commonwealth of Nations celebrates it in its own unique way, there is no uniform observance.
The precursor of Commonwealth Day was Empire Day.
It was established in 1904 and was originally celebrated in May.
After the British Empire ceased to exist and the Commonwealth of Nations (originally the British Commonwealth) was instituted, Empire Day was renamed Commonwealth Day.
This happened in 1958.
Since 1976, the holiday has been celebrated on the second Monday in March.