Question: When did Ernst Gunther, Duke Of Schleswig-Holstein's father die?

Knowledge 1: Ernst Gunther, Duke of Schleswig-Holstein
Ernst Gunther, Duke of Schleswig-Holstein (August 11, 1863 – February 22, 1921) was a son of Frederick VIII, Duke of Schleswig-Holstein and Princess Adelheid of Hohenlohe-Langenburg.He inherited his father's title as titular duke of Schleswig-Holstein.On August 2, 1898 in Coburg, he married Princess Dorothea of Saxe-Coburg and Gotha, daughter of Prince Philipp of Saxe-Coburg and Gotha and Princess Louise of Belgium.The grandfather of the bride, King Leopold II, did not attend the wedding but sent the Grand Cordon of the Order of Leopold as wedding gift.The couple had no children.However, on 11 November 1920, Ernst Gunther adopted Prince Johann Georg and his sister Princess Marie Luise, children of Prince Albrecht of Schleswig-Holstein-Sonderburg-Glücksburg. [SEP] Knowledge 2: Frederick VIII, Duke of Schleswig-Holstein
Duke Frederick VIII(July 6, 1829 – January 14, 1880) was the German pretender to the throne of Schleswig-Holstein from 1863, although in reality Prussia took overlordship and real administrative power.
Knowledge 1: Ernst Gunther, Duke of Schleswig-Holstein
Ernst Gunther, Duke of Schleswig-Holstein (August 11, 1863 – February 22, 1921) was a son of Frederick VIII, Duke of Schleswig-Holstein and Princess Adelheid of Hohenlohe-Langenburg.He inherited his father's title as titular duke of Schleswig-Holstein.On August 2, 1898 in Coburg, he married Princess Dorothea of Saxe-Coburg and Gotha, daughter of Prince Philipp of Saxe-Coburg and Gotha and Princess Louise of Belgium.The grandfather of the bride, King Leopold II, did not attend the wedding but sent the Grand Cordon of the Order of Leopold as wedding gift.The couple had no children.However, on 11 November 1920, Ernst Gunther adopted Prince Johann Georg and his sister Princess Marie Luise, children of Prince Albrecht of Schleswig-Holstein-Sonderburg-Glücksburg. [SEP] Knowledge 2: Princess Dorothea of Saxe-Coburg and Gotha
Princess Dorothea Maria Henriette Auguste Louise of Saxe-Coburg and Gotha (30 April 1881 – 21 January 1967) was a princess of Saxe-Coburg and Gotha  by birth and the duchess of Schleswig-Holstein  through her marriage to Ernst Gunther, duke of Schleswig-Holstein.Dorothea was born in Vienna, Austria, the second child and only daughter of Prince Philipp of Saxe-Coburg and Gotha and Princess Louise of Belgium.
Knowledge 1: Frederick VIII, Duke of Schleswig-Holstein
Duke Frederick VIII(July 6, 1829 – January 14, 1880) was the German pretender to the throne of Schleswig-Holstein from 1863, although in reality Prussia took overlordship and real administrative power. [SEP] Knowledge 2: Princess Dorothea of Saxe-Coburg and Gotha
Princess Dorothea Maria Henriette Auguste Louise of Saxe-Coburg and Gotha (30 April 1881 – 21 January 1967) was a princess of Saxe-Coburg and Gotha  by birth and the duchess of Schleswig-Holstein  through her marriage to Ernst Gunther, duke of Schleswig-Holstein.Dorothea was born in Vienna, Austria, the second child and only daughter of Prince Philipp of Saxe-Coburg and Gotha and Princess Louise of Belgium.

Answer: January 14, 1880