Bryan Adams wrote it with Jim Vallance, his main collaborator during many important moments, a songwriter who later also wrote for Aerosmith. Vallance has explained on his website that the song went through several changes before reaching the form we know, and that it was originally called “Best Days Of My Life,” with the phrase “Summer Of ’69” appearing only once in the lyrics. He feels that Jackson Browne’s “Running On Empty,” with the line “In ’69 I was 21,” worked as a subconscious influence on the writing, and that Adams may also have been influenced by the film Summer of ’42.