Responsa su Levitico 23:3

The problem of the changing hours of the Sabbath for changing longitudes is a very complicated one. It has recently become the subject of earnest debate and serious disagreement when the practical question arose as to when the Sabbath should be observed in Kobe, Japan, by the Jews who were exiled to the Far East a number of years ago. There is, first of all, the basic question, whether the law requires the same days be celebrated as Sabbath everywhere in accordance with the verse of Leviticus: 23:3: "It is a Sabbath unto the Lord in all your dwellings," or whether Jews should accept the civil conventions of the international date line, or other date line, if any.