29 December 1937: The new Irish Constitution - Bunreacht na hÉireann - came into effect on this day. The titles "Executive Council" and "President of the Executive Council" (a Legacy of the Treaty of 1921 with Britain) were changed to read "Government" and "Taoiseach" respectively and the separate office of President came into existence.

The Constitution of Ireland became the basic law of the State. It was adopted by plebiscite in 1937. It is the successor of the Constitution of Dáil Éireann (1919) and the Constitution of the Irish Free State (1922). The Constitution states that all legislative, executive and judicial powers of Government derive from the people. It sets out the form of government and defines the powers of the President, the two Houses of the Oireachtas and the Government. It also defines the structure and powers of the courts, sets out the fundamental rights of citizens and contains a number of directive principles of social policy for the general guidance of the Oireachtas. The Constitution may be amended only by way of referendum put to Irish Citizens resident in the State.

The new Constitution had been approved in a Referendum earlier in the year and it marked the culmination of Eamon De Valera’s attempts to undo the Anglo-Irish Treaty of 1921, which he had opposed from day one. De Valera became the first Taoiseach (Prime Minister) and Douglas Hyde the first President of Ireland or Eire - “name of the State is Éire, or, in the English language, Ireland.” - as the Free State now wished to be known. The only residue of the Treaty now left was the link to the Crown through the State’s continued and reluctant membership of the British Commonwealth – but that particular bugbear was to fall (ironically enough) to a leader of Fine Gael to accomplish in 1949.