Abstract: A clock mechanism including a fixed ring defining an inner annular surface and an outer annular surface. An hours disc is disposed to roll against one of the surfaces so as to traverse the full annular extent thereof once every twelve hours. A minute disc is disposed to roll against the other of the annular surfaces so as to traverse the full annular extent thereof once every hour. In the illustrated embodiment, the discs define planet gears, with the hours planet gear being driven by an hours sun gear so as to roll against the inner ring gear of the fixed ring. The minutes disc defines a planet gear driven by an outer ring gear to roll against the outer minute sun gear defined by the outer annular surface of the fixed ring. The fixed ring may be provided with suitable indicia to define a chapter ring.