It is good to be reminded of this story, isn't it.  What would have happened?  

Would Jews or Seventh-day Adventists have changed the calendar day for Sabbath year by year?

Well, it isn't so theoretical:

https://www.ministrymagazine.org/archive/1966/01/why-seventh-day-adventists-keep-sunday-in-tonga

And flying East to West on a missionary journey across the Pacific, one 'loses' a day give or take so what happens to the accuracy of their Sabbath keeping.  And going the other way there is a 'gain' of a day, oops.

And what happens when the evening and morning becomes uncountable at the poles of earth?

How does Seventh-day Adventist soteriology hold Sabbath?  Isn't it likely the church would have just accepted that one week a year we would just have to work an extra day before our next Sabbath rest?  It does seem a rhetorical question in the 9th decade following this historical incident.