Setting a Tide Clock Accurately

Tide clocks have an extra hand which revolves every 12 hours and 25 minutes in time with the lunar cycle. This hand is on "12 o-clock" at High Water and "6 o-clock" at Low Water. The clock uses the Lunar cycle but unfortunately the Sun also has an effect. To lessen the "error" introduced by the Sun, Tide Clocks should initially be set at a full or new moon and ideally when high water is around noon or midnight, then the effects of the Moon and Sun are synchronised.

But theres a further problem, the Lunar cycle is actually 12 hours 25 minutes and 14 seconds and whilst 14 seconds doesn't seem a lot, it's 14 seconds, twice a day or around 15 minutes a month. Over a period this adds up to a significant error. Tide Tables are the ultimate guide but if like me, you appreciate the convenience of simply glancing at a Tide Clock you may wish to endevour to keep it more accurate.

Remembering to reset the clock at each full moon is an impractical solution, here is a better idea...

From your tide table find a reference point for High Water at full moon, enter the date and time as dd/mm/yy hh:mm (gmt) in the box below then click Calculate.

This calculator takes the difference, in time, between now and your reference point, it divides this by 12 hours 25 minutes and 14 seconds then it factors in the remainder. The result is the optimal setting (as if it were a full or new moon) for today. Looking at it another way, the calculator shows us how the tide clock would be if it didn't have the 28 seconds per day error.


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