This article begins by briefly surveying the history of the cosmic week concept from its origins in pre-Christian texts through to the late eighteenth century. It then investigates its role in Millerite eschatological thought and the ways in which this impacted early Seventh-day Adventism. Between the mid-nineteenth century and early twenty-first century, the place of the cosmic week in Adventist eschatology moved from common acceptance to explicit rejection in church publications. It has recently been revived by some Adventist internet ministries, with a focus on the year 2027, seen as the end of the sixth millennium since creation and thus, it is claimed, the (approximate) date for the second coming. The biblical hermeneutics and exegesis employed to substantiate these claims are critiqued.