Possibly the only national holiday that is given recognition outside it's native land is St. Patrick's Day. This is a clear indication on the Irish influence thoughout the world. March 17th is recognised in many communities and cities as St. Patricks Day.
Everything from parades, to the 'wearing of the green' , to serving green beer (they really add green colouring to it!) to some places going as far as dying rivers green, mark the holiday of Ireland's patron saint.