User Instructions & How they work



Setting your clock

  • Obtain your local tide table and calendar with full moon information.  
  • Look up the time of today's high tide.
  • Set your clock at high tide with the hand pointing straight up.  Please note that the hand turns slowly. (Similar to the hour hand on a clock).
  • Insert your battery (Size AA).
  • On the day of the next full moon, check the accuracy of the high tide time and reset if necessary. Do not re-adjust for winter/summer time....


Setting the clock on the full moon will achieve the minimum "error" throughout the  month.  Usually the discrepancy will be less than thirty minutes and therefore will be  unnoticable, although one or two days at the first and last quarter moon may have a  greater difference. Variations equalize during each lunar month, so only check or  verify its accuracy at the full moon.




Tides are caused mainly by the gravitational pull of the Moon on the waters of the ocean.

The time taken for the Moon to reappear in the sky in the same place is called a "Lunar Day".
Your clock is based on this time scale, and rotates twice each Lunar Day. This is because most places in the world have two high tides and two low tides each day.

The Sun also plays an active role although it has less than half the influence of the Moon, because it is so much further away.

Every other week (i.e. New Moon and Full Moon) the Sun and Moon are lined up and their combined gravitational pull creates higher and lower tides.

In the intervening weeks they are at 90 degrees to each other and the Sun cancels out part of the Moon's gravitational effect. Also, at these times the Sun will make the tides somewhat earlier or later than average. 

Of course there are other factors involved which have an influence on exact tide times and it is the user's responsibility to bear these in mind. Examples which would affect a temporary increase in sea level and also change the times of high and low tides are

  • Strong on / off shore winds,
  • Atmospheric pressure (One inch difference in barometric pressure equals approximately one foot difference in sea level.),
  • Changing volume of river flows.



A mounting hole in the back allows you to  mount your clock on a single nail. Three brassed or chromed pins are provided should you wish to blank off the perimeter holes in the case.