The Longest Day consists of photographs of the sky over Los Angeles taken by David Horvitz on June 21, 2007, the day of the summer solstice, which is the longest day of the year. The images were taken around twice an hour in the same position and format, for a total of fifty photos. The progression of the images captures the gradient of daylight from one night to the next. The photos are arranged in a rather small format on the right-hand pages only and shift to the upper right, leaving plenty of white space on each page. This allows the book to be used as a flip book, which at the same time adds to the focus on capturing progression. Thus, the gradient of daylight is turned into a gradient of ink, and time is saved into a progression of pages.

Even though the photo format is rather small, the rendering of sky and light still makes for a rather lo-fi look and shows small “artifacts,” residues from digital and analog errors in the image reproduction.