Its values throughout the year are well known and are published in almanachs, calendars e.t.c. Difference in longitude between our position and the central meridian of our time zone to which usually our standard time is tuned. The central meridian of each zone is a multiple of 15 . Legal zones roughly follow this 15 limit but introduce convenient adjustments. The difference in longitude may be expressed in time units bearing in mind that 15 is equivalent to 1 hour, so 1 is 4 minutes e.t.c.
Caution has to be excersized when locating the central meridian of the time zone.
Many countries advance their Standard Time by an hour with respect to the Zone Time. Summing up we may write the relation between Local Solar Time LST and the Standard Time of the place. The equations take into account algebraic signs of corrections. Introduction of influence of daylight saving time is left to the reader. 2 shows the dial on the vertical wall with its southern normal pointing to azimuth 198 .