A complex interplay of gravitational and centrifugal forces between the earth, the moon and the sun causes the tides. On most of the earth's coasts, there are two high tides per day, always precisely 12 hours and 24 minutes apart. The Portugieser Yacht Club Moon & Tide indicates the expected times for the next high and low water on a subdial at "6 o'clock". This is achieved by a reduction wheel train which translates the regular rhythm of the hours into the constantly shifting time sequence ...