Throughout the story, time is portrayed as an unstoppable force, much like the approaching radiation cloud that will inevitably end humanity. The radiation cloud serves as a constant reminder to the characters of how little time they have left. Their frequent references to time running out—as seen in the popular refrain “not so long to go” (6)—emphasize the characters’ struggle both to make the most of their remaining time and to accept their imminent deaths. As the characters confront their mortality, they must also confront existential questions about the meaning of life, which dictates how they choose to spend their time. Some characters, like Moira, see life as essentially meaningless, and choose to spend their time partying. Others, like Mary, continue to believe that life is meaningful, but this requires a deliberate denial of reality. The novel addresses the motif of deep time when John reminds everyone that the earth isn’t ending, but it is only the end of humanity’s era. As a scientist, he marks time on a grander scale, conscious of humanity’s small blip in the world’s timeline.

As September approaches, the characters use memory to manipulate time by traveling back into the past when life was happier and more manageable.