Time and symbols of time
There are clocks and other constant references to time, like the title, which is a month's name, October. The 25 years that she has been gone are captured in the motif about time-keeping and clocks, and also in the facts of her life as she wrestles through them. Time is a symbol for decay and death, which she accepts as a kind of academic challenge, thinking through the logic of time and what it might mean.
Distance
There is a symbolic distance in the comparison that Mercia makes in her experience. She knows life in South Africa, but not the way it is currently: she only knows the South Africa of 25 years early, and she is so far away, having been in Glasgow for the last two and a half decades. She crosses a symbolic distance to come back home.
The Odyssey allusion
The novel borrows a mythic element from world literature, perhaps with The Odyssey as the pinnacle example. The story is similar to the final stage of Homer's story of Odysseus's return from the Trojan War, when he finally comes home to see what time has done to his home. For Odysseus, it was 20 years, which is pretty close, and the damage in the home is clearly similar. There are closeted commitment issues and addictions rampant in her community.
The symbolic encounter with the father
Because Mercia can't figure out which direction home is, the novel can be seen as a mythic adventure into a kind of "underworld," which is symbolized by the chaotic nature of her experience of South Africa, which should have been like a home to her. When she finally connects with her father, that isn't too dissimilar from when Aeneas encounters his own father in Hades, to solidify his identity.
Children and motherhood
Because Mercia doesn't have a child, she is an odd-ball in her South African family. Consider how obvious family seemed to the people there, but to what avail? She considers the unique challenges of motherhood in light of her modern sensibilities, analyzing her community for signs of misogyny, understanding that the home is within the domain of feminist issues. The motif is specifically also informed by the story's many, many mothers, like Netty, and all of Syvlie's mothers.
