The opening sentence of Ray Bradbury points to the irony of the clocks:
In the living room, the voice clock sang, Tick tock seven 'clock, time to get up, time to get up, seven o'clock.
With time being the invention of man, the clocks and the automatized voices are useless, for there no longer is any meaning attached to time since the residents of the house have been destroyed by an atomic blast. Nevertheless, the mindless house continues automatically to function, but its actions are futile.
The house was an altar with ten thousand attendants, big, small, servicing, attending in choirs. But, the gods had gone away and the ritual of the religion continued senselessly, uselessly.
And because the mechanical mice move senselessly, and the bath water is drawn uselessly, the house unknowingly wastes its only means of protection from the fire that begins when the cigar is lighted for no one. In the absence of the human element, the clocks now defeat the house in wasted activity as the power of nature gains control and razes the house to the ground.
With the dawn of a new day, only a solitary wall remains and the "last voice" repeats, "Today is August 5, 2026"; this date is one day before the anniversary of the dropping of the first atomic bomb, Bradbury's reminder of the danger of technology in a human world.