In April 1918, the British Cabinet, in the face of the crisis caused by the German Spring Offensive, attempted with a dual policy to simultaneously link the enactment of conscription into Ireland with the implementation of Home Rule, as outlined in the report of the Irish Convention of 8 April 1918. This further alienated Irish nationalists and produced mass demonstrations during the Conscription Crisis of 1918. In the 1918 general election Irish voters showed their disapproval of British policy by giving Sinn Féin 70%  of Irish seats, 25 of these uncontested. Sinn Féin won 91% of the seats outside of Ulster on 46.9% of votes cast, but was in a minority in Ulster, where unionists were in a majority. Sinn Féin pledged not to sit in the UK Parliament at Westminster, but rather to set up an Irish Parliament. This parliament, known as the First Dáil, and its ministry, called the Aireacht, consisting only of Sinn Féin members, met at the Mansion House on 21 January 1919. The Dáil reaffirmed the 1916 Proclamation with the Irish Declaration of Independence, and issued a Message to the Free Nations of the World, which stated that there was an "existing state of war, between Ireland and England". The Irish Volunteers were reconstituted as the "Irish Republican Army" or IRA. The IRA was perceived by some members of Dáil Éireann to have a mandate to wage war on the British Dublin Castle administration.
Question: How many years after the implementation of Home Rule did Sinn Féin members meet at the Mansion House?
Answer: 1