GG Archives Website - Link to Homepage

Changing Time At Sea (Time Zones) - 1910


At sea the ship's time changes daily, and the clocks which are usually found in the companionways are corrected. Travelers' watches should be set accordingly as the hours of meals, etc.. are dependent entirely upon these clocks.


All calculations of time are based on the sun—not the real sun that we see, but a fictitious sun that keeps better time than the real sun. The time that is indicated by a sun dial is the actual Sun Time; but this is not good enough for the civilized world because the day from noon to noon as marked by the real sun is longer at certain times of the year than at others.

However, astronomers have constructed a fictitious sun that gives us days of uniform length, and the time it marks off is called Mean Solar Time. But this does not fully solve the problem of time.

We have still to contend with the fact that the sun reaches the meridian successively later as it progresses westward. so that noon in Chicago, for instance. will be much later than noon in New York.

In fact, noon on the AVF'S t side of New York would come a few seconds later than noon on the east side. If each town in the country used local mean solar time. the utmost confusion would prevail. particularly on railroads connecting the towns. To avoid this confusion it has been found necessary to establish certain zones in which uniform time is observed.

It takes the sun twenty-four hours to circle the earth (to be sure it is the earth that moves, but for convenience we will consider that the earth is stationary and that the sun is moving around it).

The earth is divided into 360 degrees of longitude. Therefore it takes the sun one hour to traverse 15 degrees of longitude.

The United States and the majority of the European countries have decided to establish time zones approximately 15 degrees wide, so that the time of one zone will differ from the next adjacent zones by an even hour.

The degrees of longitude are measured from Greenwich, and at 15 degrees east of Greenwich the Standard Time used by the surrounding country will be just one hour ahead of Greenwich Time.

Regions in the neighborhood 30 degrees east of Greenwich will use time two hours faster than the standard time of Greenwich. The same is true in the westward direction, except that here the clocks will be set slower than Greenwich Time in even hours at intervals of 15 degrees.

Eastern Time is taken from the 75th meridian, which being five times 15 degrees west of Greenwich, makes the time in this zone five hours slower than Greenwich Time. Central Time is taken from the 90th meridian and is one hour slower than Eastern Time and six hours slower than Greenwich Time.

Mountain Time is taken from the 105th meridian, and Pacific Time from the 120th meridian. The zones are somewhat distorted, mainly to suit the convenience of railroads.

In Europe each country is small enough to be included in a single zone.
Greenwich Time is used in Belgium, Great Britain, Holland (railways and telegraph), and Spain.

Central European Time, which is one hour faster than Greenwich Time, is used by Austria-Hungary, Denmark, Germany, Italy, Norway. Servia, Sweden and Switzerland.

Eastern European Time, two hours faster than Greenwich, is used by Bulgaria and Egypt, and, by Europeans, in Turkey, the native time in the last-named country being based on sunset, which being the end of the Turkish day, marks the hour of 12.

In Belgium, Italy and Spain the clock dial is divided into twenty-four hours, beginning with 0 at midnight and thus doing away with A. M. and P. M.

A number of European countries have not accepted Standard Time based on the meridian of Greenwich, but base their time on a meridian of their own. France, for instance, uses the local mean time of Paris, which is 9 minutes and 21 seconds faster than Greenwich Time.

This is the time that appears outside of railroad stations, but the clocks inside by which the trains are operated are five minutes slower. Holland clocks are 19 minutes and 32 seconds faster than Greenwich, the time being taken from the Observatory at Amsterdam.

Ireland uses local Mean Solar Time of Dublin, and is 25 minutes and 21 seconds slower than Greenwich. Portugal takes the local Mean Solar Time of Lisbon, which is 36 minutes and 45 seconds slower than Greenwich.

As in France, railroad time is 5 minutes slower, while The Royal Observatory of St. Petersburg sets the standard for Russia, which is 2 hours 1 minute 19 seconds faster than Greenwich Time.

Were it possible for a person to travel westward around the world as fast as the sun, time would to him appear to be at a standstill. If he started, say, at noon Monday, it would always be noon Monday to him, and apparently there would be no change in his calendar. Yet some-where along his course around the world Monday must have ended and Tuesday must have begun.

Were the traveler proceeding eastward he would in 12 hours meet and pass the sun on the opposite side of the earth and would apparently have reached the hour of noon Tuesday.

At the end of 12 hours more he would meet the sun a second time and would have to tear off another leaf from his calendar and call the time noon, Wednesday. In other words, his journey around the globe would have taken him two days longer than the man who traveled with the sun and made the trip in no time.

It is a fact that a trip around the earth in a westward direction can actually be made in two days less than a trip in the eastward direction, although the same rate of speed is preserved; but the days of the east-bound traveler would be shorter than those of the west-bound traveler.

In both cases the travelers would arrive with their calendars one day wrong; but a line has been established running north and south at which travelers are obliged to add a day if they cross it going westward or subtract a day if they cross it traveling eastward. In other words, the day is supposed to start and end along this line, which is called the international Date Line.

It follows the 1140th meridian except for a few digressions, as indicated in the accompanying map, to suit the convenience of inhabitants of islands lying nearby.

Return to Top of Page

1910 Travel Guide by Scientifc American

Travel Guide Topical Index

Updates and Social Media