The song had a working title of "Traffic." Composer Justin Hurwitz told Genius
"In Damien's script, there were all the big moments, there was the big opening moment on the freeway which he described very elegantly in his script, you know… how music bubbles up from under the car radios and the girl in the first car starts humming along to it and then she gets out of her car and starts singing. And so our working title for that song, for a very long time, was just 'Traffic.' Even late in the process I remember… After Pasek and Paul wrote the words 'Another Day of Sun' and that title existed, all of the crew and department heads were still sometimes calling it 'Traffic.'"