From A Wiki of Ice and Fire
Year 282 After the Conquest (282AC) is a year in the Westerosi calendar, the 282nd after Aegon's crowning in Oldtown that maesters and educated people use as a reference to date the years.
282AC saw the birth of the first born son of Crown Prince Rhaegar Targaryen, Aegon Targaryen, though the year is better remembered by the disappearance of Lyanna Stark, which was attributed to Prince Rhaegar as him having kidnapped her. This sparked a reaction from Lyanna's eldest brother, Brandon Stark, who road to the gated of the Red Keep in King's Landing and threathened Prince Rhaegar's life. Though Rhaegar himself wasn't present, King Aerys II Targaryen was, and he ordered Brandon's arrest. Brandon's father Rickard was summoned to King's Landing as well, and in the trial that followed, both Brandon and Rickard were killed. King Aerys was not yet statisfied, however, and ordered Jon Arryn to send him the heads of Robert Baratheon and Eddard Stark, his two wards. Jon Arryn refused, and raised his banners instead. Thus began a war that would later be known under the names Robert's Rebellion, the War of the Usurper, or simply the Rebellion. The Rebellion lasted all through the year, and most of the next year, and saw some major battles.
- (Possibly) Gregor Clegane is knighted by Rhaegar Targaryen. Gregor has two possible years in which he was knighted: 281AC and 282AC. (See Gregor Clegane's Knighthood).
- Crown Prince Rhaegar Targaryen disappears with Lyanna Stark.
- Brandon Stark, while on his way to Riverrun for his wedding to Catelyn Tully, learns of Lyanna's disappearance and goes to King's Landing instead, where he is imprisoned. His companions, who had accompanied him to King's Landing, are all arrested as well.
- Rickard Stark and other nobles (200 men in total) are called to King's Landing, where they are executed with their sons.
- King Aerys II Targaryen orders Jon Arryn to send him the heads of Robert Baratheon and Eddard Stark, who had been Arryn's wards. Jon Arryn refuses, and raises his banners in revolt instead. This marks the beginning of Robert's Rebellion.
- Jon Arryn and Robert Baratheon fight the loyalist lords of the Vale in the Battle of Gulltown.
- Eddard Stark and Robert Baratheon both depart to the North and the Stormlands respectively, to raise their banners.
- The Battle of Summerhall is fought. Robert Baratheon fights three battles in one day, defeating three independent loyalist forces before they could converge upon him. The Lords Grandison, Cafferen, and Fell all fall to Robert. Fell dies, and Grandison and Cafferen are taken captive and brought to Storm's End.
- The Battle of Ashford if fought. Randyll Tarly defeats Robert Baratheon at Ashford, before the bulk of Mace Tyrells forces could arrive. Robert Baratheon is forced to flee.
- The siege of Storm's End by Lord Mace Tyrell and Lord Paxter Redwyne begins.
- Lord Owen Merryweather is fired from the office of Hand of the King. Instead, the office is bestowed upon young Lord Jon Connington.