“There is an island off the coast of New Zealand where the day of the
week changes. There Saturday is Sunday, and Sunday, Monday. When Sunday
noon closes, Monday noon begins. A man sits down to his dinner Sunday
noon, and it is Monday noon before he is done eating.”
A correspondent sends us the above statement and asks, is it correct? We
answer: Not to the islanders, who, as ourselves, have but 365 solar days
in a year. But to a stranger coming there on his voyage round the world,
who has 366 at his disposal, it is true. He has one day to spare, has no
name or place for it in the week, and just drops it out of his reckoning,
as though it had never been. The explanation is simple enough, even for
the young. The revolution of the earth on its axis, from west to east,
once in 24 hours, gives the sun an apparent motion round the earth from
east to west. To us the sun rises and sets. The succession of day and
night is just the same as if the sun really went round the earth. As the
sun’s apparent motion is from east to west, a man traveling eastward,
at whatever speed, will see the sun rise, reach the meridian, and set,
a little sooner each day than the day before. So the time indicated by
his watch, and that by the sun will differ more and more as he goes on;
and what he gains each day in time will evidently be to a solar day, as
the distance traveled is to the earth’s circumference. One degree east
will make a difference of four minutes, fifteen degrees an hour, one
hundred and eighty degrees twelve hours. Having reached the one hundred
and eightieth meridian, his chronometer and the sun are just twelve hours
apart, so he changes his reckoning, to avoid confusion, and at noon
Sunday calls it Monday. The correction is of course too much, but if he
waits till beyond that time it amounts to more than half a day, and is
constantly increasing. If the error is to be corrected all at once—and
this is the only way that is found practicable—it should be done when it
amounts to half a day. When he has completed the circuit of the earth
a whole day will have been gained. If another man, from the same place
of departure, go west, or with the sun, he will lose a day, and the
two meeting would be, if neither had changed his reckoning, two whole
days apart—yet each had the same number of hours and minutes. He who
had the greater number of days had them just so much shorter. There is,
of course, no reason in the nature of things, why the days of the week
should be changed on the one hundred and eightieth meridian rather than
elsewhere. There must be some point from which longitude is reckoned, and
to avoid confusion English and American navigators agree on Greenwich,
near London, and their nautical charts, almanacs, etc., are arranged
accordingly. If they had taken as their starting point Washington, the
one hundred and eightieth meridian would have been west of where it is,
the number of degrees between the places.