Arantar becomes King of Arnor
Event Type: Political
Age: 3rd Age - The Kings
Arantar was the son of Eldacar, and became the fifth king of Arnor at his father's death. He assumed the throne at the age of 154.
Lord of the Rings: Return of the King Appx. A Part I Section ii "The Realms in Exile"
HoME 12: The Peoples of Middle-earth Part 1 “VII The Heirs of Elendil”
The exact date is not known, but a day is set to keep the chronology correct.