How to set your Current Clock
How tide clocks work
Before you get your Current Clock set up, we want to explain how it all works.
The science
The moon moves the sea
The moon is the biggest factor in what causes tides. Its gravitational pull generates a tidal force, drawing the sea towards it. This causes a bulge, or a high tide, on the side of the Earth closest to the moon.
A matching bulge forms on the far side of the Earth too. That's why most coasts get two high tides and two low tides as the Earth turns.
The timing
Why a tide clock isn't a normal clock
24h 50m
One lunar day
The time it takes a point on the Earth to rotate from directly under the moon back to the same point under the moon. Put more simply, it's the time it takes for the moon to appear in the same place in the sky. Each full turn is called a lunar day, also known as a tidal day.
12h 25m 14s
One turn of the hand
Current Tide Clocks are designed to track the moon's effect on the tide. The hand completes a full rotation every 12 hours, 25 minutes and 14 seconds: the average time it takes the tide to come in and go out on semidiurnal coasts.
Up to 1 hour
Normal deviation
The sun affects the tides too, though not as much as the moon. So every tide clock will drift a little in accuracy through the month. Setting it at the right time keeps this to a minimum.
When to set it
Set it on a full moon or a new moon
When there's a full or a new moon, the sun, moon and Earth are in alignment. That's when high tides are at their highest and low tides at their lowest.
That's why it's so important to set your Current Clock on the day of a full or new moon, so you get the most accurate reading.
Setting up
How to set your Current Tide Clock
You'll need a tide table for your nearest coast. You can find tide tables online or in a local newspaper. We recommend tide-forecast.com.
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Find the next full or new moon
Check when the next full moon or new moon is.
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Find the time of high tide
On that date, use your tide table to find when the tide is high.
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At high tide set the hand to high tide
Move the clock hand so it points to 'High tide'.
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Put in the battery at high tide
When it's exactly high tide on the day of the full or new moon, put in the AA battery to start the clock.
Important
Don't readjust between moons
All tide clocks have deviations of up to one hour, even when set correctly. Don't readjust the clock during these deviations, as it will upset its overall accuracy. Only set the clock on the day of a full moon or new moon for accurate results.
Tide types
Where tides come twice a day
Not every coast gets the same kind of tide. On semi-diurnal coasts, including all of Ireland and Britain, there are two high tides and two low tides of about the same size in every lunar day of 24 hours and 50 minutes. That's the rhythm a Current Tide Clock follows.
Some coasts get just one high and one low tide a day, and others get two of very different sizes. Zoom in to find your coast.
Use the plus and minus keys to zoom, and the arrow keys to move around.
Curves show one lunar day: 24 hours 50 minutes