1880s|Monarch – Christian IX
Prime minister – Ditlev Gothard Monrad (until 11 July), Christian Albrecht Bluhme
February 1 – The Second Schleswig War breaks out after the First Schleswig War had left the Schleswig-Holstein Question unsettled when Treussia-Austria crosses the River Eider with 57,000 soldiers.
It soon results in the Evacuation of Danevirke.
The Battle of Sankelmark, a minor battle which occurs at Sankelmark, on the road between Schleswig and Flensburg, during the Danish retreat from Danevirke.
March 17 – The Battle of Jasmund near the Prussian island of Rügen results in a tactical Danish victory.
April 17 and 18 – Denmark suffers a severe defeat to the German Confederation in the Battle of Dybbøl which effectively decides the war.
May 9 – Denmark wins a tactical victory in the Battle of Heligoland but it has no impact on the outcome of the war.
May 12 – A general armistice came into effect, Denmark has lost the war.
June 29 – In the Battle of Als, the last major engagement of the war, the Prussians secure Als after a night attack masterminded by the Chief of Staff Leonhard Graf von Blumenthal,
July 3 – The Battle of Lundby in north-eastern Himmerland results in great Danish losses. It becomes the last battle of the Second Schleswig War.
July 8 – The Cabinet of Monrad is succeeded by the Cabinet of Bluhme.
October 30 – The Second Schleswig War ends. The Duchies of Schleswig, Holstein and Lauenburg are ceded to Prussia.
May 6 – Jens Christian Kofoed, architect (died 1941)
May 15 – Vilhelm Hammershøi, painter (died 1916)
May 23 – Louis Glass, composer (died 1936)
July 12 – Carl Brummer, architect (died 1953)
November 15 – Sophus Falck, manufacturer and founder of Falck (died 1926)
March 28 – Princess Louise Charlotte, princess of Denmark (born 1789)
September 7 - Gustav Friedrich Hetsch, architect (born 1788)
October 20 – Carl Christian Rafn, historian, translator and antiquarian (born 1795)
1864 in Denmark Wikipedia
Events from the year 1864 in Denmark.