Sir Gawain and the Green Knight
How we cite our quotes:
When the siege and the assault were ended at Troy,
The city laid waste and burnt into ashes […]
(1 - 2)
The narrator of Sir Gawain begins his story after the fall of Troy - approximately 2000 years before the action begins. Why might he do this? Well, in order to get to Arthur, he has to go through a "history lite" version of the founding of Britain and the kings leading up to Arthur, which allows him to locate Arthur as part of a prestigious and long-lasting tradition of bravery, making him (and the stories surrounding him, like the narrator’s) seem very important, since they form a part of this tradition.
And when Britain had been founded by this noble lord,
Valiant men bred there, who thrived on battle.
In many an age bygone, they brought about trouble.
More wondrous events have occurred in this country
Than in any other I know of, since that same time.
But of all those who dwelt there, of the British kings
Arthur was always judged noblest, as I have heard tell.
(20 - 26)
This passage sets Arthur (and the story) in the "age bygone" in which more wondrous events have occurred than in any other. This "bygone age" is a little like "once upon a time" - we know to expect a universe similar to ours, but one in which anything - like fairies, ogres, and giant green men - is possible.
For there the festival lasted the whole fifteen days
With all the feasting and merry-making that could be devised:
Such sounds of revelry splendid to hear,
Days full of uproar, dancing at night.
(44 - 47)
Sir Gawain opens during the Christmas season at Arthur’s court, which, in the traditional church calendar, lasted a full fifteen days. During that time, the court gathers for the length of the whole celebration.