Charles Presley, age 14, of Thomaston# Ga., for his question:
Where does the day begin?
More than half a century after Magellan, the Golden Hind put into Plymouth. She too had sailed around the world. But the ships log did not tally with the calendars at home. Captain Francis Drake seemed to have lost a day. Drake did penance for failing to observe the proper saints days and most people assumed that he had just forgotten to record one day of his long voyage.
This, of course, was not so. Drake had sailed westward all the way. Had he sailed eastward he would have gained a day on his voyage around the world. For the earth turns towards the east, one complete turn every 24 hours. In sailing around westward, Drake had canceled out the complete turn of the earth and so lost a calendar day, Had he sailed eastward, in the same direction as the turning earth, he would have added a circle and so gained a calendar day,
The earth pays no attention to man‑made calendars. Midnight over the Atlantic is noon over the Pacific. And at every moment a new day is beginning somewhere on the earth's surface. So man, who invented the calendar, had to fix a spot where every date, every new calendar day, should begin. This should be a meridian running from pole to pole and far from densely settled areas. For one calendar day would be ending on one side of this line and a new calendar day beginning on the other side. It would be possible to step from Tuesday to Wednesday and back again ‑ very confusing to the business people in a real city.
The right spot was selected by sailors. Seafarers of many nations developed a custom of changing dates as they crossed Longitude 130 degrees, also called the Prime Meridian. This date changing line is called, of courses. The International Date Line. It was not settled by an international committee, however. The world merely followed the sensible custom of the sailors. Later it was adjusted in a few places and it now only roughly follows the Prime Meridian. In the north,, the Date Line jogs to the west so as to include Alaskaand some of the Aleutians in the American date zone.
South of the equator it jogs to the east in order to include the Fijis and other south sea islands in the same date zone as Australia.
A calendar day lasts from midnight to midnight. And each new calendar day is born on the Date Line. From this point it travels westward around the earth and ends on the eastern side of the Date Line. Wednesday noon on the western side is Tuesday noon on the eastern side. Crossing from the east, Tuesday noon becomes Wednesday noon. Crossing from the west, Wednesday noon becomes Tuesday noon.
A traveler around the world loses or gains a calendar day a bit at a time. In a journey across America, he crosses four time zones. Travelling westward he sets his watch back an hour with every time zone. Travelling eastward, he sets his watch forward an hour with every time zone. On a trip around the globe there are 24 such time zones ‑ enough to gain or lose an entire day, The date of the whole calendar day is adjusted as he crosses the International Date Line, on or near the Prime Meridian. For this is where each new calendar day begins and ends.