The eight-day clock and the 30-hour clock were among the first clocks to begin replacing the traditional weight-driven clocks during the late 1600s. Eight-day clocks continued to be manufactured until modern times, and many traditional clock workshops still produce eight-day models.
Many clocks contain a tightly coiled spring that provides the force necessary to move the gears of the clock. Eventually the spring uncoils to the point where the clock gears no longer move and the clock spring must be "wound" in order to re-tighten it so that the clock will resume operation.
