The way the author of the old poser proposed to solve the difficulty was
as follows: From the Jew's abode let the Christian and the Turk set out
on a tour round the globe, the Christian going due east and the Turk due
west. Readers of Edgar Allan Poe's story, _Three Sundays in a Week_, or
of Jules Verne's _Round the World in Eighty Days_, will know that such a
proceeding will result in the Christian's gaining a day and in the
Turk's losing a day, so that when they meet again at the house of the
Jew their reckoning will agree with his, and all three may keep their
Sabbath on the same day. The correctness of this answer, of course,
depends on the popular notion as to the definition of a day--the average
duration between successive sun-rises. It is an old quibble, and quite
sound enough for puzzle purposes. Strictly speaking, the two travellers
ought to change their reckonings on passing the 180th meridian;
otherwise we have to admit that at the North or South Pole there would
only be one Sabbath in seven years.