"John Perkins looked at the clock. It was 8.15" Why is the time significant?"The Pendulum" by O. Henry.

In O. Henry's short story, "The Pendulum," there is a routine of activities that occur after John Perkins arrives home from riding the elevated train from work with the "citizen sheep" who descend toward their homes.

The metaphor of "sheep" in the exposition of O. Henry's story is significant because, like sheep, Perkins and his wife follow a diurnal routine that has reduced them--to use a cliche--to creatures of habit.

Part of Perkins's routine of adjusting to the movements of the neighbors after supper is to go to McCloskey's for a game or two of pool "with the fellows":

John Perkins knew these things would happen.  And he knew that at a quarter past eight he would summon his nerve and reach for his hat, and that his wife would deliver this speech in a querulous tone:  'Now where are you going, I'd like to know, John Perkins.'

However, when Perkins arrives home one night, his wife is not home to greet him, things are not in their usual place.  After he finds a note, he is "dazed" by the break in routine, just as a sheep would be dumbfounded by any change in routine.  Sitting down to a cold, lonely meal after setting the room aright, John Perkins, who "was not accustomed to analysing his emotions," begins to realize how much his wife really does mean to him; he vows to be more appreciative and spend time with her in the evenings.

However, when she suddenly returns, saying that her mother's condition which took her away, was not serious enough for her to remain the narrator states,

Nobody heard the click and rattle of the cog-wheels as the third-floor front of the Frogmore flats buzzed its machinery back into the Order of Things.  A band slipped, the spring was touched, the gear was adjusted and the wheels revolve in their old order.

With the metaphor of the clock, O. Henry implies that the "old order" of the Perkins's routine is reestablshed.  The sheep, John Perkins, looks at the clock which reads "8:15."  This is the time for his nightly visit to McCloskey's.  Yet, despite his momentary resolve to be more attentive to his wife, Perkins in his conditioning for sheepish routine repeats his machine-like statement, "Thought I'd drop up to McCloskey's" and falls back into his sheep-like existence.