It would be more sensible to use the date of the founding of the Irish Free State on 6th December 1922 as this took place by formal and internationally recognised agreement.
It might even be more sensible to use 18 April 1949 as this is the date when the Republic of Ireland Act 1948 came into force, which removed the remaining constitutional role of the British monarch.
She lives in London, the eternal capital of England, not London the capital of suburban prairie beyond Hamilton and Kitchener, Ontario.
True, Canada still uses the Royal Assent in lawmaking (unlike Australia and New Zealand, for example, which have abandoned it but retain the Queen as Head of State) but in that capacity the Queen is acting as Queen of Canada, not Queen of the UK
Thanks for sharing.