Question: Elisabeth of Bavaria's husband was born on what date?

Context paragraphs:
Maria Sophie of Bavaria: Maria Sophie in Bavaria, (4 October 1841, Possenhofen Castle – 19 January 1925, Munich) was the last Queen consort of the Kingdom of the Two Sicilies.  She was one of the ten children of Maximilian Joseph, Duke in Bavaria and Princess Ludovika of Bavaria.  She was born as Duchess Maria Sophia in Bavaria.  She was the younger sister of the better-known Elisabeth of Bavaria ("Sisi") who married Emperor Franz Joseph I of Austria.

Duke Pius August in Bavaria: Duke "Pius August" in Bavaria, full German name: "Pius August Herzog in Bayern" (born 1 August 1786 in Landshut, Electorate of Bavaria; died 3 August 1837 in Bayreuth, Kingdom of Bavaria) was a Duke in Bavaria as a member of the Palatine Birkenfeld-Gelnhausen line of the House of Wittelsbach.  Pius August was a grandfather of Empress Elisabeth of Austria through his son Duke Maximilian Joseph in Bavaria, as well as a great grandfather of Queen Elisabeth of the Belgians and an ancestor of the current generations of the Belgian and Italian Royal Families and the Grand Ducal Family of Luxembourg .

Elisabeth of Bavaria, Queen of Belgium: Elisabeth of Bavaria (born "Duchess Elisabeth Gabriele Valérie Marie in Bavaria") (25 July 187623 November 1965) was Queen consort of the Belgians as the spouse of King Albert I, and a Duchess in Bavaria by birth.  She was the mother of King Leopold III of Belgium and of Queen Marie-José of Italy, and grandmother of kings Baudouin and Albert II of Belgium.

Elisabeth of Bavaria, Queen of Germany: Elisabeth of Bavaria (  1227 – 9 October 1273), a member of the House of Wittelsbach, was Queen consort of Germany from 1246 to 1254 by her marriage to King Conrad IV of Germany.

Princess Amélie Louise of Arenberg: Princess Amélie Louise d'Arenberg, full German name: "Amalie Luise, Prinzessin und Herzogin von Arenberg" and full French name: "Amélie Louise, princesse et duchesse d'Arenberg", (born 10 April 1789 in Brussels, Austrian Netherlands; died 4 April 1823 in Bamberg, Kingdom of Bavaria) was a member of the House of Arenberg by birth and, through her marriage to Duke Pius August in Bavaria, a member of the Palatinate-Birkenfeld-Gelnhausen line of the House of Wittelsbach.  Amélie Louise was a grandmother of Empress Elisabeth of Austria through her son Duke Maximilian Joseph in Bavaria.

Duke Wilhelm in Bavaria: Duke "Wilhelm" in Bavaria, full German name: "Wilhelm, Herzog in Bayern" (born 10 November 1752 in Gelnhausen, Palatinate-Birkenfeld-Gelnhausen; died 8 January 1837 in Landshut or Bamberg, Kingdom of Bavaria) was Count Palatine of Birkenfeld-Gelnhausen between 1789 and 1799 and first Duke in Bavaria from 16 February 1799 until his death in 1837.  From 17 December 1803 to 20 March 1806, Wilhelm was titled Duke of Berg.  Wilhelm was a great-grandfather of Empress Elisabeth of Austria through his son Duke Pius August in Bavaria.

Richardis of Jülich: Richardis of Jülich (1314–1360) was a daughter of Gerhard V of Jülich and Elisabeth of Brabant-Aarschot.  She married Otto IV, Duke of Lower Bavaria, son of Stephen I, Duke of Bavaria, with whom she had one child: Albert of Wittelsbach, who was born in 1332.  He predeceased his father.  Her husband died in 1334.

Princess Elisabeth, Duchess in Bavaria: Princess Elisabeth, Duchess in Bavaria (born 31 December 1940) is the wife of Prince Max, Duke in Bavaria, heir presumptive to both the former Bavarian Royal House and the Jacobite Succession.

Conrad IV of Germany: Conrad (25 April 1228 – 21 May 1254), a member of the Hohenstaufen dynasty, was the only son of Emperor Frederick II from his second marriage with Queen Isabella II of Jerusalem.  He inherited the title of a King of Jerusalem (as Conrad II) upon the death of his mother in childbed.  Appointed Duke of Swabia in 1235, his father had him elected King of Germany (King of the Romans) and crowned King of Italy (as Conrad IV) in 1237.  After the emperor was deposed and died in 1250, he ruled as King of Sicily (Conrad I) until his death.

Prince Leopold of Bavaria (born 1943): Prince Leopold (Poldi) of Bavaria (German: "Leopold Rupprecht Ludwig Ferdinand Adalbert Friedrich Maria et omnes sancti Prinz von Bayern" ) (born 21 June 1943) is a member of the Bavarian royal house of Wittelsbach and a former champion race car driver.  He descends from King Ludwig I of Bavaria in direct line and is a distant relative to the current head of the House of Wittelsbach, Franz, Duke of Bavaria and his brother, Maximilian, Duke in Bavaria.  He also descends from Austrian Emperor Franz Joseph and his wife Elisabeth and from King George II of Great Britain, and is therefore a distant cousin of Elizabeth II.  As a Roman Catholic he is excluded from the line for the British throne by the Act of Settlement 1701.  He also descends from Isabella II of Spain, through her daughter, and Leopold´s great-grandmother, María de la Paz.

Supporting paragraphs: Elisabeth of Bavaria, Queen of Germany Conrad IV of Germany
Answer: 25 April 1228