You should understand a little about what causes the high and low tides. The moon is the major cause of the tides. The lunar day, the time it takes for the moon to reappear at the same place in the sky, is 24 hours and 50 minutes. Most locations have two distinct high tides and two low tides each day. Therefore, the hand on our tide clocks rotates once every 12 hours and 25 minute, twice each lunar day. The Tide Clock will always stay in exact step with the moon. But there are many other factors that can make the day-to-day tides a little earlier or later than the Tide Clock shows. It is impossible for us to determine these conditions for your locality. The sun also affects the tides, but has less than half the influence of the moon. When the sun, moon and earth are lined up, as they are at time of the new moon and full moon, their influences combine and high tide is higher than normal and low tide is lower than normal. When the sun and the moon are at right angles, as they are at the first quarter and last quarter of the moon, the sun cancels some of the moon's effect and the range of tide is smaller than normal. At these times the sun will cause the tides to be somewhat earlier or later than average. This is why it is so important to first set your Tide Clock on the day of a full moon, as the moon has the dominating effect on the tides