It states that Tidal Predictions are in the Standard Local Time Zone of the place concerned. What does this mean, and how do these Time Zones work?
Universal Time (UT) is the mean solar time of the prime meridian obtained from direct astronomical observation and corrected for the effects of small movements of the Earth relative to the axis of rotation. Greenwich Mean Time (GMT) is based on the hour angle of the mean sun and for all tidal predictions may be taken as the same as UT. The term UT(GMT) is used throughout this volume. There are twenty four Time Zones in the world each of which covers 15° of longitude. The zero time zone, in which the time kept corresponds to Greenwich Mean Time, is centred on the prime meridian and extends from 7.5°W. to 7.5°E. The other zones, in which the time kept differs from GMT by an integral number of hours, are sequentially numbered and have either a negative prefix if east of Greenwich or a positive prefix if west of Greenwich. To convert Zone Time to GMT, the number of hours as given by the zone number is added to or subtracted from the Zone Time, e.g. in Zone – 0400 the time kept is 4 hours i
