This is a little harder to understand. Perhaps you don't know that the date does change—but if it didn't, then when it is Sunday on one side of the earth it would be Monday on the other.

Turn your orange-earth over slowly and watch the light rays strike one side after another. Remember, day is always beginning somewhere. It is always noon somewhere, always night, and it takes twenty-four hours for any one spot on the earth to go through all the changes of morning, noon, evening, midnight.

Since this is true, the people of the great trading nations had to agree on a place where a new day should begin for everybody. You see they needed to date letters and telegrams, newspapers and business papers of all sorts. It wouldn't do to have a date-changing line pass through a big city, or even through a country where many people lived'. For it would make no end of trouble to say it was Monday on the west side of a busy street, and Tuesday on the east side. A place was chosen to run a date line north and south, away out in the middle of the Pacific Ocean.

Cut a line on the skin of the orange-earth from where the hatpin goes in, at one end, to where it goes out at the other. We'll call that the date line; although, as a matter of fact, the real dateline is not straight up and down, but zigzags about among islands. It goes half way around the earth, up and down the very widest ocean. Now continue the line around, dividing the earth into two halves. On the line exactly opposite the date line stands London, the greatest trading and banking city on earth, with 6,000,000 people living in it. There, time and dates are very important, so the trading nations agreed to keep London time—that is, to date everything by time in London, and to correct the date on the exactly opposite side of the earth, in mid-ocean.

Pretend you are in London at noon, Monday. You are a giant with seven-league boots on. You start around the world westward, traveling as fast as the earth turns eastward. It is noon all the way around. But, as the journey takes twenty-four hours, you get back to London at noon the next day. Now, go around the earth eastward, travelling just as fast as before, against the sun, or in the same direction as the earth. You will meet the sun at noon, when half way around, and in half a day, or twelve hours. You pass the sun and meet it again at noon, in London, twelve hours later. As you had noon-time twice in twenty-four hours, you must count Monday twice. So you lose a day, or have the same day twice in going around the earth eastward, and gain or skip a day in going around westward. When crossing the date line, ships going eastward count the same day twice ; westward going ships skip a day to keep their dating correct with London time.