question: When did William I, Duke Of Brunswick-Lüneburg's father die?
context: [["Frederick William, Duke of Brunswick-Wolfenb\u00fcttel", ["Frederick William, Duke of Brunswick-Wolfenb\u00fcttel (9 October 1771 \u2013 16 June 1815) was a German prince and Duke of Brunswick-L\u00fcneburg and Oels.", "Nicknamed \"The Black Duke\", he was a military officer who led the Black Brunswickers against French domination in Germany.", "He briefly ruled the state of Brunswick-Wolfenb\u00fcttel from 1806 to 1807 and again from 1813 to 1815."]], ["Henry III, Duke of Brunswick-Grubenhagen", ["Henry III, Duke of Brunswick- L\u00fcneburg(* 1416 Grubenhagen, \u2020 20 December 1464), of the House of Welf, was a Duke of Brunswick- L\u00fcneburg ruling the ducal Principality of Grubenhagen between 1427 and 1464."]], ["Elizabeth of Denmark, Duchess of Brunswick-Wolfenb\u00fcttel", ["Elisabeth of Denmark (25 August 1573 \u2013 19 July 1625) was duchess consort of Brunswick-L\u00fcneburg as married to Duke Henry Julius of Brunswick-L\u00fcneburg.", "She was regent of Brunswick-L\u00fcneburg in 1616-1622."]], ["Francis Otto, Duke of Brunswick-L\u00fcneburg", ["Francis Otto, Duke of Brunswick- L\u00fcneburg( 1530 \u2013 1559) was the Prince of L\u00fcneburg from 1555 to 1559.", "He was the son of Ernest I, Duke of Brunswick- L\u00fcneburg."]], ["Matilda of Brunswick-L\u00fcneburg", ["Matilda of Brunswick- L\u00fcneburg( 1276 \u2013 26 April 1318) was a German noblewoman and member of the House of Welf.", "By birth, she was a duchess of Brunswick- L\u00fcneburg and by marriage Duchess of Glog\u00f3w, \u015acinawa, etc.", "She was the seventh child and only daughter of Albert I, Duke of Brunswick- L\u00fcneburg by his second wife Alessina, daughter of Margrave Boniface II of Montferrat."]], ["Dorothea of Brunswick-L\u00fcneburg", ["Dorothea of Brunswick-L\u00fcneburg (1 January 1570 \u2013 15 August 1649) was a daughter of Duke William \"the younger\" of Brunswick-L\u00fcneburg and his wife, Dorothea of Denmark, Duchess of Brunswick-L\u00fcneburg.", "She married Count Palatine Charles I of Zweibr\u00fccken-Birkenfeld.", "They had four children:"]], ["Duke Louis Ernest of Brunswick-L\u00fcneburg", ["Louis Ernest of Brunswick- L\u00fcneburg- Bevern( 25 September 1718, Wolfenb\u00fcttel \u2013 12 May 1788, Eisenach) was a field- marshal in the armies of the Holy Roman Empire and the Dutch Republic, the elected Duke of Courland( 1741).", "From 13 November 1750 to 1766 he was the Captain- General of the Netherlands, where he was known as the Duke of Brunswick or( to distinguish him from his eldest brother Charles, who succeeded to their father's title of Duke of Brunswick- L\u00fcneburg) Duke of Brunswick- Wolfenb\u00fcttel.", "Another brother was Duke Ferdinand of Brunswick who led the Allied Anglo- German army during the Seven Years' War.", "He was probably one of the first victims of the media in Dutch history."]], ["Albert I, Duke of Brunswick-L\u00fcneburg", ["Albert the Tall (1236 \u2013 15 August 1279), a member of the House of Welf, was Duke of Brunswick-L\u00fcneburg from 1252 and the first ruler of the newly created Principality of Brunswick-Wolfenb\u00fcttel from 1269 until his death."]], ["William I, Duke of Brunswick-L\u00fcneburg", ["William (c. 1270 \u2013 30 September 1292 in Brunswick), Duke of Brunswick-L\u00fcneburg, briefly ruled part of the duchy.", "William was the third son of Albert I, Duke of Brunswick-L\u00fcneburg.", "On Albert's death on 1279, the three eldest brothers succeeded him, but were put under guardianship of Conrad, Prince-Bishop of Verden.", "After they reached majority, they divided the territory among each other in 1291:", "William received the northern part of their father's state, including Brunswick, Sch\u00f6ningen, the Harzburg, Seesen, and K\u00f6nigslutter.", "The brothers disagreed over control of the City of Brunswick.", "Only a year later, William died, and his brothers divided his territory among each other.", "He had married Elizabeth, daughter of Henry I, Landgrave of Hesse, but the marriage apparently remained childless."]], ["Henry the Peaceful, Duke of Brunswick-L\u00fcneburg", ["Henry the Peaceful( 1411 \u2013 7 December 1473), Duke of Brunswick- L\u00fcneburg, called the Peaceful, ruled over both parts of Brunswick- L\u00fcneburg."]]]
supporting_facts: [["William I, Duke of Brunswick-L\u00fcneburg", 1], ["Albert I, Duke of Brunswick-L\u00fcneburg", 0]]
evidences: [["William I, Duke of Brunswick-L\u00fcneburg", "father", "Albert I, Duke of Brunswick-L\u00fcneburg"], ["Albert I, Duke of Brunswick-L\u00fcneburg", "date of death", "15 August 1279"]]
answer: 15 August 1279