The Durin's Day event is low live in LOTRO! Available through October 20th, turning off at 3:00am Eastern (-4 GMT) on October 21st.
Durin's Day is a rare event as observed by the Longbeards; the clan founded by Durin - the first day of the Dwarves New Year, when both the Sun and Moon may be seen in the sky together.
The Moon-letters written on the map that Gandalf had received from Thráin II, as read by Elrond, instructed, 'Stand by the grey stone when the thrush knocks, and the setting sun with the last light of Durin's Day will shine upon the key-hole.' (Thus revealing the secret door into the Lonely Mountain).
The new year of their calendar was the last cycle of the Moon to begin in Autumn, or in Thorin's words 'the first day of the last moon of Autumn on the threshold of Winter. We still call it Durin's Day when the last moon of Autumn and the sun are in the sky together.'
'Stand by the grey stone when the thrush knocks," read Elrond, "and the setting sun with the last light of Durin's Day will shine upon the key-hole." "Durin, Durin!" said Thorin. "He was the father of the fathers of the eldest race of Dwarves, the Longbeards, and my first ancestor: I am his heir." "Then what is Durin's Day?" asked Elrond. "The first day of the dwarves' New Year," said Thorin, "is as all should know the first, day of the last moon of Autumn on the threshold of Winter. We still call it Durin's Day when the last moon of Autumn and the sun are in the sky together. But this will not help us much, I fear, for it passes our skill in these days to guess when such a time will come again."
In The History of The Hobbit, Tolkien set 19 October as the date of that year's Durin's Day. Originally added to the game in 2018 players who visit the memorial stone will be auto-bestowed the quest Durin's Day Upon Erebor. Completion of this quest will unlock the Observer of Durin's Day title as well as other deeds if this is your 2nd or 3rd year of visiting respectively. The memorial stone is a dwarf carved stone on the side of the Lonely Mountain at the secret door.