"A Rose for Emily" is really tricky because Faulkner tells the story out of order; it takes some very close reading, note-taking, and time-lining in order to figure out just exactly when things happened, and in what time-frame. Fortunately, this answer is sitting right there, in the first sentence of section II. It states, "So she vanquished them, horse and foot, just as she had vanquished their fathers thirty years before about the smell." The tax men visited her, and she "vanquished" them; she kicked them out of her house, and refused to pay the taxes. Faulkner states that this event occurred thirty years after the smell did. So, thirty years earlier, when these taxmen were just little kids probably, the house had smelled, and the townsfolk had to, in the dark of night, spread lime around the house to get rid of the smell.
I hope that answers your question adequately; good luck!