In this era of tweets and blogs, it is easy to assume that the self-obsessive recording of daily minutiae is a recent phenomenon. But Americans have been navel-gazing since nearly the beginning of the republic. The daily planner—variously called the daily diary, commercial diary, and portable account book—first emerged in colonial times as a means of telling time, tracking finances, locating the nearest inn, and even planning for the coming winter. They were carried by everyone from George Washington to the soldiers who fought in the Civil War. And by the twentieth century, this document had become ubiquitous in the American home as a way of recording a great deal more than simple accounts. This history of the daily act of self-reckoning explores just how vital these unassuming and easily overlooked stationery staples are to those who use them. From their origins in almanacs and blank books through the nineteenth century and on to the enduring legacy of written introspection, the author has penned a biography of an almost ubiquitous document that has borne witness to American lives in all of their complexity and mundanity.