Definition of Irony
When Eckels first sees the Time Machine, he imagines using it to escape the results of yesterday's election had the outcome been different. In entertaining the possibility, Eckels foreshadows the irony of the story's ending:
A real Time Machine […] Makes you think. If the election had gone badly yesterday, I might be here now running away from the results. Thank God Keith won. He’ll make a fine President of the United States.
When Eckels returns to the year 2055, he notices a subtle change in the atmosphere and finds that the English language now uses a different spelling system. After finding the culprit of such changes—a crushed butterfly on the bottom of his shoe—he realizes the irony of his situation:
Unlock with LitCharts A+“Not a little thing like that! Not a butterfly!” cried Eckels. It fell to the floor, an exquisite thing, a small thing that could upset balances and knock down a line of small dominoes and then big dominoes and then gigantic dominoes, all down the years across Time.