Crossing the Line

MAN HAS LONG DREAMED OF TRAVELING through time to relive the past or to see the future. So would it surprise you to know that in a sense people travel through time every day? Consider the businessman from Tokyo who jets to New York for a meeting. If his flight departs at noon, then after flying nonstop nearly halfway around the world, he will land at his destination that same morning, seemingly earlier than he left.

Is it really possible to take a long trip and yet arrive before you leave? No, not really. But distant cities are in different time zones. In fact, crossing the international date line, an invisible line on the globe, means crossing an agreed upon boundary that separates calendar days. Talk about a disorienting experience! Depending on which direction you travel, it’s like gaining or losing one day in an instant.

Suppose that for his return flight, the Tokyo businessman leaves New York late Tuesday evening. When he steps off the airplane some 14 hours later, it will already be Thursday in Japan. How strange it feels to skip a whole day! One seasoned traveler, recalling her first trip across the international date line, confessed: “I could not understand where that missing day went. It was so peculiar.”

Because the date line can befuddle travelers, some may wonder why such a demarcation was ever contrived.

Sailors Make a Discovery

The need for a date line is evident if we look back to 1522, when the crew of Ferdinand Magellan completed the first circumnavigation of the earth. After three years at sea, they reached Spain on Sunday, September 7. According to their ship’s logbook, however, the date was Saturday, September 6. Why the discrepancy? By sailing around the world in the same direction as the sun, they had witnessed one less sunrise than the people of Spain.

Author Jules Verne utilized the reverse of this phenomenon as a plot twist for his novel Around the World in Eighty Days. To win a large sum of money, the main character in that book had to travel completely around the earth in 80 days. At the  end of his adventure, he arrived home disappointed, just one day too late to collect his sizable reward. Or so it seemed to him. He was astonished to learn that, in reality, he had met his deadline. As the book explains, “Phileas Fogg had, without suspecting it, gained one day on his journey, and this merely because he had travelled constantly eastward.”

While it may seem that the international date line gave Mr. Verne’s story a happy ending, the line did not actually exist in its present form when the famous novel was published in 1873. Sea captains of that time would routinely make a one-day calendar adjustment while crossing the Pacific Ocean, but the present date line did not appear on their maps. This was prior to the adoption of a universal system of time zones. Thus, when Alaska was a possession of Russia, people there followed the same calendar day as the residents of Moscow. But in 1867, when the United States purchased the territory, Alaska adopted the calendar date of the United States.

Historical Developments

In 1884, amid this timekeeping chaos, representatives from 25 nations met in Washington, D.C., for the International Prime Meridian Conference. They established a worldwide system of 24 time zones and agreed upon a prime meridian—the longitude line passing through Greenwich, England. * It became the starting point for measuring east-west positions on the globe.

Halfway around the earth from Greenwich—12 time zones away heading east or west—seemed like a logical spot for an international date line. Although not officially adopted by the 1884 conference, the 180-degree meridian gained acceptance as an especially suitable location because it assured that the date line would not pass through a continent. Can you imagine what confusion would result if it were Sunday in one half of the nation where you live and Monday in the other half?

If you consult a world atlas or globe, the 180-degree meridian can be found to the west of Hawaii. You will notice immediately that the international date line does not follow the meridian exactly. It cuts a zigzag path through the Pacific Ocean to avoid land entirely. And because the date line was established by general agreement, not by international treaty, it is subject to change at the whim of any nation. In 1995, for example, Kiribati declared that the international date line, which cut through that chain of islands, would henceforth take a detour around that nation’s easternmost island. Today’s up-to-date maps therefore show all the islands of Kiribati on the same side of the line. Thus, they share the same calendar day.

How It Works

To illustrate why a day is either lost or added when crossing the date line, imagine that you are sailing around the world. And let’s say that you are heading east. You might not be aware of it, but you are considered to be gaining one hour for each time zone that you travel through. When you finally complete your trip around the world, you will have traveled through 24 time zones. Without an international date line, you would be considered a day ahead of local time. The international date line corrects this discrepancy. It’s a little confusing, isn’t it? No wonder that Magellan’s crew and the fictitious Phileas Fogg miscalculated the date they completed their journeys around the world!

Those who have crossed the line are acquainted with the strange feeling of suddenly losing or gaining a day. But travel would be even more confusing if it were not for the international date line.

[Footnote]

^ par. 11 For more information about time zones and longitude lines, see the March 8, 1995, Awake! article “Those Useful Imaginary Lines.”

[Diagram/Map on page 13]

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[Pictures on page 14]

Above: Greenwich Royal Observatory

Right: This cobblestone line marks the prime meridian