Final answer:
The setting for 'Sir Gawain and the Green Knight' falls between 1350 and 1400 A.D. during the Late Middle Ages, a period that encompassed the Hundred Years' War and the development of Middle English literature, including chivalric romances and works like Geoffrey Chaucer's 'The Canterbury Tales.'
Step-by-step explanation:
The setting of the narrative poem Sir Gawain and the Green Knight is approximately between 1350 and 1400 A.D. This time frame situates the tale squarely in the period known as the Late Middle Ages, characterized by the cultural and political turmoil of the Hundred Years' War and marked by the flowering of chivalric tales involving knights and their adventures. The text itself is written in Middle English, the form of English prevalent from 1150 to 1500 A.D., which was characterized by a variety of dialects and orthographic practices.
During this same period, significant historical events such as England's King Edward III's claim to the French throne led to the extended conflict of the Hundred Years' War underlining the chaotic yet romanticized context in which knights like those in the Arthurian legends, including Sir Lancelot and Sir Gawain, were celebrated. The period also saw English literature flourish with works like Geoffrey Chaucer's The Canterbury Tales, laying the literary groundwork for the Gawain poet and his contemporaries.