Commonwealth Day

WordReference Random House Unabridged Dictionary of American English © 2025

Com′monwealth Day′, 

1. a holiday observed in some countries of the Commonwealth of Nations, originally on May 24, the anniversary of Queen Victoria's birth, but now on varying dates. Formerly, Empire Day. 

• 1955–60

Collins Concise English Dictionary © HarperCollins Publishers::

Commonwealth Day noun

1. the anniversary of Queen Victoria's birth, May 24, celebrated (now on the second Monday in March) as a holiday in many parts of the Commonwealth
   Former name: Empire Day