Three Consecutive Sabbath Days on Same Day

Problem

 * Christians the week's first day for Sabbath hold.
 * The Jews the seventh, as they did of old,
 * The Turks the sixth, as we have oft been told.
 * How can these three, in the same place, and day,
 * Have each his own true Sabbath, tell, I pray.

It perhaps needs to be elaborated that:
 * The word Sabbath is taken to mean religious holy day, whatever that day might be, rather than the more contemporary meaning of just Saturday
 * The first day of the week is taken to be Sunday, rather than the more contemporary understanding of this being Monday
 * Hence the sixth and seventh days are Friday and Saturday, considered as the holy day of the week by Muslims and Jews respectively
 * In the milieu in which this question was asked, Turk was understood as being synonymous with Muslim, which is no longer an accurate position to hold.

Solution
The three travel (or not) as follows.
 * The Jew stays where he is.
 * The Christian travels around the world towards the east.
 * The Turk travels around the world towards the west.

When they meet again, it is (according to the Jew) Saturday.

But:
 * the Christian has lost a day because those days are shorter
 * the Turk has gained a day because those days are longer.

So by their own reckoning:
 * according to the Christian, it is Sunday
 * according to the Turk, it is Friday.

Note of course that in the modern world, they will have taken into account the, which has the effect of resetting the date so that it is globally consistent.

Also see

 * Horses Born and Died at Same Time but with Different Ages, a variant of this