What is a Tide Clock?

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  • Written By: Rachel Burkot
  • Edited By: Bronwyn Harris
  • Last Modified Date: 08 October 2019
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A tide clock is a clock that indicates the times of the next high and low tides by keeping track of the moon’s motion around the earth. Tide clocks use a tide dial and solar time dial, which are rotated at different rates by a timepiece. The time of the next tide is indicated by the alignment of indicia, identifying marks, on the dials.

Using a tide clock is a good way to learn about the cycle of the ocean and its ebb and flow. The clock can predict ocean activity, and tide predictions can be made thirty years in the future. The user can add or subtract about six hours to determine when the tide is next going to be high or low. A tide clock keeps track of tides through moon time, in which one day equals 24 hours and 50.5 minutes. These nautical clocks keep track of the rate, on average, between high lunar tides, which come 12 hours and 24 minutes apart, or about half of a lunar day.

A tide clock works in almost any ocean location, but it must be reset each time it is moved. Tide clocks are most reliable on the East Coast of the United States and Canada because tides are most predictable there. They also work on the West Coast of the United States and in other countries, but they must be used with special setting tables. Tide clocks do not work in the Gulf of Mexico.


The tide clock was invented in 1971 by Louis Schelling of Newton, New Jersey. It is useful for boaters, surfers, swimmers, sailors, fishermen, seaside home owners and beach-goers. The bottom of a tide clock is marked “low tide,” and the top is marked “high tide.” The left is marked “hours until high tide,” while the right is marked “hours until low tide.” The countdown is marked by a red ball hand, which always shows how many hours until the next local high or low tide.

A tide clock’s data can be displayed in different graphical views. Tide clocks can also be personalized with art, photographs or charts. The ocean clocks are set for the time where the local high tide occurs, so it is different at every location. Also, lunar and solar tides fall in and out of sync during a lunar month. A tide clock is synchronized to the moon’s daily cycle, so using these clocks can be a good way to learn about tides, ocean patterns and lunar cycles.


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