Question: When was the father of Albert, Duke of Schleswig-Holstein born? 

Context paragraphs:
Prince Christian of Schleswig-Holstein: Prince Christian of Schleswig-Holstein (Frederick Christian Charles Augustus; 22 January 1831 – 28 October 1917) was a minor Danish-born German prince who became a member of the British Royal Family through his marriage to Princess Helena of the United Kingdom (25 May 1846 – 9 June 1923), the fifth child and third daughter of Queen Victoria and Prince Albert of Saxe-Coburg-Gotha.

Albert II, Duke of Bavaria: Duke Albert II or Albrecht (1368 – January 21, 1397, Kelheim) was a feudal co-regent, with his father Albert I, Duke of Bavaria, in the counties of Holland, Hainaut, and Zeeland in the Low Countries.  Additionally, from 1389 until his death in 1397, he administered the Bavarian province of Straubing in the name of his father, it being his Bavarian ducal line's appanage and seat.  Albert II's mother was Margaret of Brieg, great granddaughter of Wenceslaus II of Bohemia.

Albert II, Duke of Saxony: Albert II of Saxony (Wittenberg upon Elbe, ca. 1250 – 25 August 1298, near Aken) was a son of Duke Albert I of Saxony and his third wife Helen of Brunswick and Lunenburg, a daughter of Otto the Child.  He supported Rudolph I of Germany at his election as Roman king and became his son-in-law.  After the death of their father Albert I in 1260 Albert II jointly ruled the Duchy of Saxony with his elder brother John I, and thereafter with the latter's sons.

Albert, Duke of Schleswig-Holstein: Albert, Duke of Schleswig-Holstein (Albert John Charles Frederick Alfred George; 26 February 1869 – 27 April 1931), was a grandson of Queen Victoria.  He was the second son of Victoria's daughter, Princess Helena, by her husband Prince Christian of Schleswig-Holstein.  He was the head of the House of Oldenburg and also the House of Schleswig-Holstein-Sonderburg-Augustenburg and the Duke of Schleswig-Holstein between 1921 and 1931.

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 (German: "Prinzessin von Sachsen-Coburg und Gotha" ) by birth and the duchess of Schleswig-Holstein (German: "Herzogin zu Sachsen" ) 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.

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.

University of Kiel: The University of Kiel (German: "Christian-Albrechts-Universität zu Kiel", CAU) is a university in the city of Kiel, Germany.  It was founded in 1665 as the "Academia Holsatorum Chiloniensis" by Christian Albert, Duke of Holstein-Gottorp and has approximately 26,000 students today.  The University of Kiel is the largest, oldest, and most prestigious in the state of Schleswig-Holstein.  Until 1864/66 it was not only the northernmost university in Germany but at the same time the 2nd largest university of Denmark.  Faculty, alumni, and researchers of the University of Kiel have won 12 Nobel Prizes.  The University of Kiel is a member of the German Universities Excellence Initiative since 2006.  The Cluster of Excellence The Future Ocean, which was established in cooperation with the GEOMAR Helmholtz Centre for Ocean Research Kiel in 2006, is internationally recognized.  The second Cluster of Excellence "Inflammation at Interfaces" deals with chronic inflammatory diseases.  The world-renowned Kiel Institute for the World Economy is also affiliated with the University of Kiel.

John I, Duke of Saxony: Duke John I of Saxony (1249 – 30 July 1285, Wittenberg upon Elbe) was the elder son of Duke Albert I of Saxony and his third wife Helen of Brunswick and Lunenburg, a daughter of Otto the Child.  John and his younger brother Albert II jointly ruled the Duchy of Saxony after the death of their father Albert I in 1260.

Agnes Bernauer: Agnes Bernauer (c. 1410 – 12 October 1435) was the mistress and perhaps also the first wife of Albert, later Albert III, Duke of Bavaria.  Because his father, Ernest, ruling Duke of Bavaria at the time, considered this liaison with a commoner unbefitting his son's social standing, he clashed with his son over the matter and finally arranged to have Agnes condemned for witchcraft and drowned in the Danube in 1435.  Her life and death have been depicted in numerous literary works, the most well known being Friedrich Hebbel's tragedy of the same name and the folk musical "Die Bernauerin" by the composer Carl Orff.

Christoph, Prince of Schleswig-Holstein: Christoph, Prince of Schleswig-Holstein (born 22 August 1949) has been the head of the House of Schleswig-Holstein-Sonderburg-Glücksburg (commonly known as the House of Glücksburg) and, by agnatic primogeniture, of the entire House of Oldenburg since 1980.  He is the current titular Duke of Schleswig-Holstein and Duke of Glücksburg, traditionally styled as "His Highness".  He is a male-line descendant of Christian III of Denmark, and is also descended cognatically from numerous more recent monarchs, including Queen Victoria, Emperor Alexander II of Russia and several more recent Danish kings.

Supporting paragraphs: Albert, Duke of Schleswig-Holstein Prince Christian of Schleswig-Holstein
Answer: 22 January 1831