On 1^stDecember 1847 the Pope Pio IX introduced the use of marking the time with a cannon in order to have only one signal for the official time rather than the uncoordinated sound of the bells of Churches.

The tradition continued with the unification of Italy. The cannon fired until August 1903 from its first position in Castel Sant'Angelo; it was then moved to the slopes of Monte Mario and finally to Gianicolo on 24^th January 1904.

During the Second World War the tradition was interrupted because of the war.

On 21^st April 1959, in occasion of the 2712 Anniversary fro​m the foundation of Rome, the cannon started again to mark the "noon" for the roman citizens.

The type of cannon used until August 1904 is unknown. Since then a cannon of 75 mm was used, the same employed by the Artillery of the Kingdom of Italy to open the breach of Porta Pia.

Then an howitzer of 149/13 was used; its gun tube, war booty of the Austro-Hungarian Army in the 1915-1918 war, was installed on an Italian gun carriage.

On 1^st February 1991, that cannon fired its last shot.

Now it is used an howitzer resulted from the assembly of the 105/22gun tube with the 88/27 gun carriage used during the World War II.

The service squadron, firstly provided by the 8^th CERIMANT of Rome, is always made available by the Army.