What is the setting of Dirk Gently's Holistic Detective Agency by Douglas Adams?

The novel's settings are diverse, including a space ship orbiting above the Earth, an alien planet, the fictional St. Cedd's College in Cambridge, billions of years ago in what is now Bermuda, and modern-day London. These settings are far-flung from each other, in time as well as in space. However, the story ties all these wide-ranging settings together into a single storyline revolving around the moment when the novel begins, the moment when life begins on Earth.