The structure of Sir Gawain and the Green Knight is completely governed by time. The story begins on New Year’s Eve, during the Christmas feast at King Arthur’s Court. Gawain must meet the Green Knight at the Green Chapel in a year and a day. The Christmas at Sir Bertilak’s feast lasts three days, followed by three days in which Gawain sleeps late while Bertilak goes on hunts, the timing of which is bookended by sunrise and sunset. The poem’s obsession with time yields a beautiful description of the passing of the seasons. The point of this seems to be that there’s a set time for everything, and that time brings change in its wake. More than that, time forces destiny for human beings, with its passing drawing Gawain ever closer to the day on which he must meet his fate at the hands of the Green Knight.
The poem’s section on the seasons links Gawain to the animals and plants it describes in the way the passing of time dictates the behavior of all of them.
Sir Gawain’s focus of time is intimately linked to its respect for customs and traditions in its attention to the "proper" time for things like feasting, celebrating, eating, and sleeping.