In our first lesson we spoke about time in general. We will now consider a special kind of time, namely, True Local Time. This is the same as Sun Time, which is gauged by the instant when the Sun crosses the meridian (when it is directly overhead) at any particular place. This instant marks True Local Noon for that place. We will also learn how to convert Standard Time, the prevailing time in the United States, into True Local Time.
Prior to November 18, 1883, the time used in any particular locality was Sun Time, that is, True Local Time.
But since that time it has been found convenient to substitute what is called Standard Time, for Sun Time, particularly in America, and therefore the student should understand the division of the country into time zones, so that he may be able to make necessary corrections when calculating horoscopes for dates subsequent to the institution of Standard Time.
This innovation grew out of the confusion which existed in railroad time-tables before its introduction. Where several railroads entered a city, each had its clocks set to a standard of its own, and in addition, the people in that city had their own local time. Sometimes the clock on one railway station varied half an hour from that of another railroad company, and both pointed to a different time from the timepiece on the city hall. It was therefore suggested that if the country be divided into time zones, each about fifteen degrees of longitude in width (this being the distance the Sun travels in one hour), and all the clocks in each division set to one uniform time, gauged by a meridian located in the center of its time zone, the difficulty would be overcome. Accordingly, America was divided into four such zones by three imaginary lines, as illustrated in the diagram:
center of its time zone, the difficulty would be overcome. Accordingly, America was divided into four such zones by three imaginary lines, as illustrated in the diagram:
In the Eastern Time Zone clocks are set to the 75th Meridian, 5 hours earlier than Greenwich Mean Time.
In the Central Time Zone time is regulated to the 90th Meridian, which is 6 hours earlier than Greenwich.
In the Mountain Time Zone timepieces are governed according to the 105th Meridian, which is 7 hours earlier than Greenwich Mean Time.
In the Pacific Time Zone time is set to the 120th Meridian, 8 hours earlier than Greenwich.
In all cities located on these Standard Meridians (indicated by arrows on our diagram), such as Philadelphia and Denver, Standard Time is also the True Local Time, and no correction is required in calculation of horoscopes. But Detroit, which you will see located near the dividing line between the Eastern and Central Time Zones, is 8 degrees west of the 75th Meridian, and its clocks are therefore 32 minutes faster than Sun Time, for when they show noon according to the 75th Meridian Standard, the True Local Time is 32 minutes before twelve. Chicago you see a little east of the 90th Meridian (2 degrees). When the clocks there are at twelve, it is really 8 minutes past the noon hour. San Francisco clocks show noon when the True Local Time is only 11:50 A.M., because that city is 2 1/2 degrees west of the Standard Meridian. Correction is therefore necessary because True Local Time must be used in all subsequent calculations of the horoscope. The rule for obtaining True Local Time is: to the nearest Standard Meridian Time, add four minutes for each degree the birth place is east of the Meridian corresponding to that Time. If the birth place is West of that Meridian, subtract four minutes for each degree it is West thereof.
To illustrate, we will find the True Local Time for a birth at New York, July 23, 1912, 5:56 AM, Standard Time. By reference to the map we find that New York is in about 74 degrees West Longitude, which is one degree east of the nearest Standard Time Meridian, namely, the 75th meridian. Following our rule, we add one times four, or four minutes to the time shown by the clock (5:56 A.M.), obtaining thereby 6:00 AM, which is the True Local Time of birth.
Similarly, for a birth at New York, July 28, 1912, 9:56 PM, we find that the True Local Time is 1000 PM.
Note specially, however, that this correction of Standard to True Local Time applies only to the United States and is required only for dates subsequent to Nov. 18, 1883, when Standard Time was adopted. But, in such other countries as have special time regulations, these must be taken into account in calculating True Local Time.
Was this article helpful?