DisturbedNeo tem a data correta; Celeborn e Galadriel assumiram o controle político de Lothlórien em torno de T.A. 1980 ou 1981. A data vem até nós de Contos Inacabados , que contém um histórico detalhado do par da Segunda Era em diante. Há dois rascunhos concorrentes descrevendo o evento:
It was not until far on in the Third Age, when Amroth was lost and Lórinand was in peril, that Galadriel returned there, in the year 1981.
Unfinished Tales Part 2: "The Second Age" Chapter IV: "The History of Galadriel and Celeborn"
[I]t was not until the disaster in Moria [T.A. 1980], when by means beyond the foresight of Galadriel Sauron's power actually crossed the Anduin and Lórien was in great peril, its king lost, its people fleeing and likely to leave it deserted to likely occupied by Orcs, that Galadriel and Celeborn took up their permanent abode in Lórien, and its government.
Unfinished Tales Part 2: "The Second Age" Chapter IV: "The History of Galadriel and Celeborn" Amroth and Nimrodel
O primeiro rascunho é datado por Christopher Tolkien para aproximadamente a escrita do O Senhor dos Anéis , mas ele não é mais específico do que isso; pode ser a qualquer momento de 1937 a 1949. O segundo esboço é datado de 1969 e provavelmente representa os pensamentos finais (registrados) de Tolkien sobre o assunto em sua vida.
No entanto
Eu sinto que é importante ressaltar que Galadriel foi nunca Rainha de Lórien; isso é algo que Tolkien sentiu a necessidade de chamar especificamente, então eu acho que vale a pena ser claro (ênfase minha):
After the disaster in Moria [in the year 1980] and the sorrows of Lórien, which was now left without a ruler (for Amroth was drowned in the sea in the Bay of Belfalas and left no heir), Celeborn and Galadriel returned to Lórien, and were welcomed by the people. There they dwelt while the Third Age lasted, but they took no title of King or Queen; for they said that they were only guardians of this small but fair realm, the last eastward outpost of the Elves.
Unfinished Tales Part 2: "The Second Age" Chapter IV: "The History of Galadriel and Celeborn" Amroth and Nimrodel