Why does the author of Grendel manipulate time?

The novel is divided into twelve different chapters, each chapter representing each of the twelve zodiac symbols. The story begins in the spring and works its way through the seasons. Coinciding with the seasons is Grendel’s annual interactions with the humans. Spring, summer, and fall are all seasons when Grendel raids Hart. Winter is his downtime, but he still keeps an eye on the town below. Over the course of Grendel’s moral changes, he struggles with the ideas of whether he agrees with humanity’s unwavering faith or if humanity is being too hopeful for their future.

Many of the chapters break from the traditional narrative prose form and instead opt to tell the story in a different way. There are sections of poetry, play dialogue, and even songs to heighten the novel’s art theme. These narrative forms also give Gardner the chance to explore his main character and express himself more freely.