A People's Calendar (aPC) is an open-source project that seeks to promote the worldwide history of working class movements and liberation struggles in the form of a searchable "On This Day" style calendar.
The Piazza Fontana Bombing was a false flag, fascist terrorist attack in Milan that occurred on this day in 1969, committed by "Ordine Nuovo" with help from police. The attack was blamed on anarchists and led to the death of Giuseppi Pinelli.
Image: The office and counter area inside the Banca Nazionale dell'Agricoltura in Milan after the explosion [italyonthisday.com]