There is something odd going on with the international date line. I saw that the Radvaz deals with this question. He first was asked if it is one period in time everywhere, - and he says no. Because the first shabat was in the Sinai desert. Therefore, it is to each individual according to his place. And then he brings the question of where the day starts, and he brings the same sources as the Chazon Ish, the Kuzari and the seder Olam who say it starts in the far east ( after the end of the continent, not in the middle). so everything is clear. It does not start in the exact opposite of Jerusalem, but rather somewhere in the middle of the Pacific Ocean . To me this means everything is clear. But the Chazon Ish held a different day that what is set by the international date line. He starts the day exactly opposite Jerusalem and he says he based this on the Kuzari and seder Olam. To me it seems that if the middle of longitude is in Greenwich Mean Time (GMT), then the date line is in the middle of the Pacific Ocean, and that the day starts at the very far end of the far east (Just like the Goyim say). But take a look at a map. If you assume Jerusalem is in the middle, and the day starts on the exact opposite side, then the date line is in the middle of Asia and then yom kipur comes out a different day. Then, Rav Isar Zalman Metlzar said, “The Chazon Ish was wrong.” The complaint that the Chazon Ish said about this was that Rav Izar Meltzar did not write this in his book on the Rambam. But if you look at the introduction to his book, the Even HaAzael, you will see that Rav Meltzar said openly that he did not include in his book the ideas that he said the yeshiva. The book is focused only on the Rambam. The fact that an important decision was left out means nothing. i also saw in the radvaz an issue that occurred to me --the problem of having the ketubah written and signed before the actual wedding-that is a document that is able to be collected on before the date of it time when it is valid in fact. Thet ketubah not valid. I did not read and learn the whole answer of the radvaz in depth, but years ago I decided that since my own ketutbah was written and signed in such a way it was not valid and wrote another one for my wife