25 April is a public holiday in Italy. It is the day on which Italy celebrates its liberation from German occupation in 1945 (and the people and organizations involved to end it) and the end of 20 years of Fascism.
Since history is not a one-day-event, the 25 April was picked to mark a historically important development rather a specific point in time. It is a convenient choice because it coincided with the liberation of Milan and Turin by partisans and the official beginning of the insurrection against German occupation and the fascist regime by means of a general strike. The call was issued by the leadership of the CLNAI via radio at 8am on 25 April 1945.
Proclamation of general strike by Sandro Pertini (here).