Sir Gawain and the Green Knight depicts a world in many ways rooted in the world of the fourteenth century; however, it shares a great deal with the world of earlier centuries, including the period with which Beowulf is associated.
At the opening of Sir Gawain and the Green Knight, the reader is brought into a world where lavish banquets are in many ways the norm. Reading the description of the fortnight-long celebration at the court of Camelot is strikingly reminiscent of the early scenes at Heorot in Beowulf. Like Hrothgar, King Arthur presides over the proceedings at the hall in Camelot, demanding the respect of those in attendance. As in Beowulf, the festivities at Camelot are interrupted by a "monstrous" visitor, the Green Knight.
The Green Knight's arrival at Camelot introduces another point of comparison between the two poems. In Beowulf, the warriors abide by the warrior code, the fundamental tenets of which are loyalty, generosity, bravery, courage, and valor, among others. In Sir Gawain and the Green Knight, the knights adhere to the code of chivalry, and specifically to the idea of courtesy. The code of chivalry is an outgrowth of the warrior code, as it, like it predecessor, praises bravery and courage in battle, as well as loyalty. The major points of departure lay in the greater importance of religion to the world of Sir Gawain and the Green Knight. The knights observe Christian virtues, something the warriors in Beowulf do not do consistently. In addition, chivalry, and specifically courtesy, elevates the importance of women in fourteenth-century society. As such, part of the code of courtesy is that a knight must adhere to the requests of a lady. The code of chivalry also demands fealty to one's lord. In Beowulf, fealty to one's lord did not derive from the importance of a code but from the importance of the lord's actions.
When the Green Knight proposes the bargain to the knights at Camelot, they all sit in stunned silence. King Arthur, though somewhat reluctant, finally declares that he will accept the challenge. Sir Gawain, however, takes up the challenge in the king's place. As part of the code, it is the king's duty to be the first to take up a challenge; the other part of the code is that another knight must stand to defend his king.
Generally, what is seen in Sir Gawain and the Green Knight is an outgrowth of the practices present in Beowulf. The code of chivalry reflects many of the same characteristics prized among the warriors of earlier centuries; the main difference is that that behavior has become codified.