14 events the sources record for this year, grouped by region.
What happened
China (8)
Youzhou troops rebelled, killed Zhu Kerong and his son, and set up his second son Zhu Yansi as Youhou. (Old Book of Tang (Jiu Tangshu), Annals 舊唐書 卷17上 寶曆2年)
Eunuchs led by Wang Shoucheng put the Prince of Jiang (later Wenzong) on the throne, executed Liu Keming, and enthroned him at the Xuanzheng Hall. (New Book of Tang (Xin Tangshu), Annals 新唐書 卷008 穆宗~宣宗 寶曆2年12月)
Minister of the Right Fujiwara no Otsugu says that the memorial of the first year of Tenchō fixed Balhae visits at one cycle of twelve years, yet they now break that limit on the strength of Lingxian's words; he proposes sending them back. Others object that the fine story of the emperor's abdication should be made known overseas. (Nihon Kōki (Later Chronicles of Japan) 日本後紀 卷34)
Taesu Baek Yeong of Ujam mobilized ten thousand people from the Hanbuk districts and built a three-hundred-li long wall at Paegang. (Samguk Sagi (History of the Three Kingdoms) 卷10 憲德王 18年)
When King Heungdeok ascended, envoys soon brought a pair of parrots from the Tang; when the female died, the male saw its reflection in a mirror and died. (Samguk Yusa (Memorabilia of the Three Kingdoms) 紀異第二 興德王鸚鵡)
Western Europe (5)
At the end of January in Aachen the emperor meets his son Pippin, king of Aquitaine, and the counts of the Spanish frontier; they deliberate and decide how to guard the western frontier against the Saracens (Royal Frankish Annals ARF a.826, Kurze 1895 p.169)
In mid-May the emperor leaves Aachen, and in early June holds an assembly at Ingelheim, where he receives envoys of the papal curia: Bishop Leo, Theophylactus, Dominicus, abbot of Mount Olivet, and the envoys of the sons of Godofrid of Denmark and of the Abodrite chiefs (Royal Frankish Annals ARF a.826, Kurze 1895 p.169)
Danish King Heriold, with his wife and many Danes, is baptized at the church of St Alban in Mainz on June 24, receives the emperor's gifts, and goes back to Frisia, where he receives a county (Royal Frankish Annals ARF a.826, Kurze 1895 p.170)
After the autumn hunt the emperor crosses the Rhine to the Zalca villa, where he meets envoys from Neapolis. News comes that Aeizo, a figure of the Spanish frontier, fled and entered Ausona, destroyed the city of Lota, and gained the help of the Saracen king Abdirraman (Royal Frankish Annals ARF a.826, Kurze 1895 p.170)
At the mid-October assembly of Ingelheim, Ceadragus and Tunglo are interrogated. Tunglo, after giving a son as hostage, is sent home; Ceadragus is kept back and, after asking the will of the Abodrite people and taking hostages, is restored (Royal Frankish Annals ARF a.826, Kurze 1895 p.171)