Tide Clock Frequently Asked Questions

How does a tide clock work ?

The moon is the prime influence on tides. The time from one moonrise to the next is approximately 24 hours and 50 minutes, unlike the sun whose cycle is 24 hours . This is why the time of the next high tide is not the same each day.
The sun also affects the tides, but has less than half the influence of the moon. So when the sun, moon and earth are all lined up, as they are at times of new moon and full moon, their gravitational influences co-incide, making the high tide, higher, and the low tide, lower. When the sun and the moon are at right angles, during the first and last quarters of the moon, the sun cancels some of the moon’s effect and the range of tide is smaller than normal. Also, at these times the sun’s gravitational pull makes the tides come earlier or later than usual, which is why the tide clock can be up to half an hour out.

This is why it is IMPORTANT for optimum accuracy to first set your Tide Clock at the high tide on the day of a full moon. The clock does not tell you how high the tide will be, only when the next tide will happen. The Shapel Tide Clock is for areas which have a semi-diurnal tide cycle, ie 2 high tides a day.

Will it work in my area?

Because tides all over the world rely on the cycle of the moon, it doesn’t really matter where you are. The time-tide clock will work anywhere in the world as long as the tides are regular. Most places have two high tides and two low tides each day. But local currents and landforms can change that. You should check your local area. If you do not have regular tides, the tide clock may not work. Known areas for this are Shark Bay in Western Australia and Portland in Victoria, where occasionally only one change of tide occurs. And some parts of the west coast of the USA
Test: Your tides are regular if:
The high tide from one day to the next keeps getting later by about 48 minutes: for example, if we take the morning high tide on a Tuesday, if it is at 10am, then on the next day, Wednesday, it will be 10:48am (There may, of course be 2 high tides within the day)

What about Daylight Saving?

The tide clock tells you how long until the next tide, not what time it will occur. Therefore it is not affected by daylight saving.