What is the song Last Kiss by Taylor Swift about?

I think it's about Joe Jonas, but don't quote me on that. In her song "Better than Revenge" (about Camilla Belle stealing Joe from her) she sings, "The story starts when it was hot and it was summer" & in "Last Kiss" she sings, "That July 9th/The beat of your heart/It jumps through your shirt/I can still feel your arms", which leads me to believe both songs have something to do with Joe.