Question: Æthelstan Half-King left his position and became a monk after the death of a king who ruled England starting which year ?

full_context: Document 1: Eadric, Ealdorman of Wessex: Eadric (fl. 942–949) was a tenth-century ealdorman of Wessex. He was the youngest of four sons of Æthelfrith, an ealdorman in Mercia, and his wife Æthelgyth. From 946 until his death in 949 Eadric was the second most senior ealdorman in England, surpassed only by his brother Æthelstan Half-King.
Document 2: Ælfhere, Ealdorman of Mercia: Ælfhere (died in 983) was ealdorman of Mercia. His family, along with those of Æthelstan Half-King and Æthelstan Rota, rose to greatness in the middle third of the 10th century. In the reign of Edward the Martyr, Ælfhere was a leader of the anti-monastic reaction and an ally of Edward's stepmother Queen Dowager Ælfthryth. After the killing of Edward by Ælfthryth's servants in 978, Ælfhere supported the new king, Ælfthryth's son Æthelred the Unready, and was the leading nobleman in the Kingdom of England until his death in 983.
Document 3: Edgar Ætheling: Edgar Ætheling (also spelt Æþeling, Aetheling, Atheling or Etheling) or Edgar II (c. 1051 – c. 1126) was the last male member of the royal house of Cerdic of Wessex (see House of Wessex family tree). He was proclaimed, but never crowned, King of England in 1066.
Document 4: Edward the Exile: Edward the Exile (1016 – 19 April 1057), also called "Edward Ætheling", was the son of King Edmund Ironside and of Ealdgyth. He spent most of his life in exile in the Kingdom of Hungary following the defeat of his father by Canute the Great.
Document 5: Edward the Elder: Edward the Elder (Old English: "Eadweard cyning "; c. 874 – 17 July 924) was King of the Anglo-Saxons from 899 until his death. He became king in 899 upon the death of his father, Alfred the Great. He captured the eastern Midlands and East Anglia from the Danes in 917 and became ruler of Mercia in 918 upon the death of Æthelflæd, his sister.
Document 6: Eadred: Eadred (also Edred) (923 – 23 November 955) was King of the English from 946 until his death. He was the son of Edward the Elder and his third wife Eadgifu of Kent, and a grandson of Alfred the Great. Eadred came to the throne following the assassination of his older brother, Edmund I. The chief achievement of his reign was to bring the Kingdom of Northumbria under total English control, which occurred with the defeat and expulsion of Eric Bloodaxe in 954. Eadred died at the age of 32 having never married, and was succeeded by his 15-year-old nephew, Eadwig.
Document 7: Æthelweard (son of Alfred): Æthelweard (d. 920 or 922) was the younger son of King Alfred the Great and Ealhswith.
Document 8: Ealdgyth, daughter of Earl Ælfgar: Ealdgyth ("fl. c". 1057–1066), also Aldgyth or in modern English, Edith, was a daughter of Ælfgar, Earl of Mercia, the wife of Gruffudd ap Llywelyn (d. 1063), ruler of all Wales, and later the wife and queen consort of Harold Godwineson, king of England in 1066. She was described by William of Jumièges as a considerable beauty.
Document 9: Æthelred the Unready: Æthelred II, also dubbed the Unready (Old English: Æþelræd, ] ), (  966 – 23 April 1016) was King of the English (978–1013 and 1014–1016). He was the son of King Edgar the Peaceful and Queen Ælfthryth and was around 12 years old when his half-brother Edward the Martyr was murdered on 18 March 978. Although Æthelred was not personally suspected of participation, the murder was committed at Corfe Castle by his attendants, making it more difficult for the new king to rally the nation against the military raids by Danes, especially as the legend of St Edward the Martyr grew.
Document 10: Edward the Confessor: Edward the Confessor (Old English: "Ēadƿeard Andettere" ] , Latin: "Eduardus Confessor" ] ; c. 1003 – 5 January 1066), also known as Saint Edward the Confessor, was among the last Anglo-Saxon kings of England. Usually considered the last king of the House of Wessex, he ruled from 1042 to 1066.
Document 11: Ealdgyth (floruit 1015–1016): Ealdgyth (circa 992 – after 1016), modern English Edith may have been the name of the wife of Sigeferth son of Earngrim, thegn of the Seven Burghs, and later of King Edmund Ironside. She was probably the mother of Edmund's sons Edward the Exile and Edmund Ætheling.
Document 12: Edmund Ironside: Edmund II (died 30 November 1016), usually known as Edmund Ironside, was King of England from 23 April to 30 November 1016. He was the son of King Æthelred the Unready and his first wife, Ælfgifu of York. Edmund's reign was marred by a war he had inherited from his father, his cognomen "Ironside" was given to him "because of his valour" in resisting the Danish invasion led by Cnut the Great.
Document 13: Æthelstan Half-King: Æthelstan (fl. 932 - 956), was an important and influential Ealdorman of East Anglia who interacted with five kings of England, including his adopted son Edgar the Peaceful. Many of Æthelstan's close relatives were also involved in important affairs, but soon after the death of king Eadred in 955, he left his position and became a monk at Glastonbury Abbey.
Document 14: Ancestry of the Godwins: Very little is known for certain of the ancestry of the Godwins, the family of the last Anglo-Saxon King of England, Harold II. When King Edward the Confessor died in January 1066 his closest relative was his great-nephew, Edgar the Ætheling, but he was young and lacked powerful supporters. Harold was the head of the most powerful family in England and Edward's brother-in-law, and he became king. In September 1066 Harold defeated and killed King Harald Hardrada of Norway at the Battle of Stamford Bridge, and Harold was himself defeated and killed the following month by William the Conqueror at the Battle of Hastings.
Document 15: Edmund Ætheling: Edmund Ætheling ( ;  1015–17 – possibly 1046, certainly by 1054) was a member of the royal House of Wessex as the son of Edmund Ironside, who briefly ruled as King of England between April and November 1016. He fought the Danish Vikings under Cnut the Great, but following the Danish victory at the Battle of Assandun in October, it was agreed that Ironside would rule Wessex, while Cnut took Mercia and probably Northumbria. In November 1016, Ironside died and Cnut became King of all England.
ground_truth: 946