I have to agree with llscience in the way that it's about the perfect beginning of a relationship, but you also have to look at the name of the song, september, which is the beginning of fall and traditionally fall symbolizes death or an ending, not saying that this means the author thinks the relationship will end soon. Just saying that it's supposed to be about the ending of the perfect part of a relationship that's about to hit its darker times, which kind of fits the tone of the song in my opinion.
I have to agree with llscience in the way that it's about the perfect beginning of a relationship, but you also have to look at the name of the song, september, which is the beginning of fall and traditionally fall symbolizes death or an ending, not saying that this means the author thinks the relationship will end soon. Just saying that it's supposed to be about the ending of the perfect part of a relationship that's about to hit its darker times, which kind of fits the tone of the song in my opinion.