These are all symbols of time in the story. What's more, the struggle between the past and the future threatens to rip the present to pieces. When members of the Board of Aldermen visit Emily to see about the taxes a decade before her death, they hear her pocket watch ticking, hidden somewhere in the folds of her clothing and her body. This is a signal to us that for Miss Emily time is both a mysterious "invisible" force, and one of which she has always been acutely aware. With each tick of the clock, her chance for happiness dwindles .
Another symbol of time is Emily's hair. The town tells time first by Emily's hair, and then when she disappears into her house after her hair has turned "a vigorous iron-gray, like the hair of an active man" (4.6). When Emily no longer leaves the house, the town uses Tobe's hair to tell time, watching as it too turns gray. The strand of Emily's hair found on the pillow next to Homer, is a time-teller too, though precisely what time it tells is hard to say. The narrator tells us that Homer's final resting place hadn't been opened in 40 years, which is exactly how long Homer Barron has been missing. But, Emily's hair didn't turn "iron-gray" until approximately 1898, several years after Homer's death.
In "What's up With the Ending?" we suggest that the town knew they would find Homer Barron's dead body in the room. But maybe what they didn't know was that she had lain next to the body at least several years after its owner had departed it, but perhaps much more recently. Still, the townspeople did have to break into the room. When and why it was locked up is probably only known by Emily (who is dead, and wouldn't talk anyway) and Tobe (who has disappeared, and wouldn't talk anyway).
The stationery is also a symbol of time, but in a different way. The letter the town gets from Emily is written "on paper of an archaic shape, in a thin, flowing calligraphy in faded ink" (1.4). Emily probably doesn't write too many letters, so it's normal that she would be using stationery that's probably at least 40 years old. The stationery is a symbol, and one that points back to the tensions between the past, the present, and the future, which this story explores.