While this short story by Hemingway is a "slice of life" story, there is also a shattering metaphoric significance to the meaning of the title. For the father it is the twenty-four hour period to keep watch on his son's fever; however, for the son, who misunderstands the severity of his fever because he thinks his temperature has been measured in Celsius rather than Farenheit degrees, the waiting through one day has a deeply existential meaning.
The climax, or high point of interest or suspense in the story, comes when Schatz asks, "About how long will it be before I die?"His father replies,
"You aren't going to die. What's the matter with you?'
Oh, yes, I am. I heard him say a hundred and two."
The poor boy has been alone, believing his fever so high that he will die because the students at the French school he has attended once spoke of no one surviving a temperature of forty-four degrees, and Schatz did not know that they spoke of degrees in Celsius. Therefore, when the boy asks his father this question, the father is filled with regret that he has left the boy because he knows his child has been alone with his fear of death, holding himself under control all those hours.