The electronics inside the clock precisely measure the 24 hours, 50 minutes and 30 seconds of a lunar day. The gravitational pull of the moon, along with local other factors, is what creates tidal movement. This synchronisation between the tide and the moon is very regular but there will be small variations during each month. We would expect that, between full moons, your Tide Clock (or any Tide Clock) might be at most, 30 - 60 minutes out. Returning back to accuracy again as the averages converge once more. Because of this, fine tuning or adjustment during the month is not recommended. You can read more in our Tide Clock instruction manual here.