Photo Credit: Mosaica Press

Title: Crossing the Dateline (3 Volumes)
Author: Rabbi Mordechai Kuber
Publisher: Mosaica Press



In Crossing the Dateline – a monumental work – Rabbi Mordechai Kuber gives the halachic dateline the sophisticated treatment it deserves. He holds the reader’s hand while tackling this intricate topic and translates complex discussions into plain English.

Throughout the three volumes that comprise this work – particularly in volume I – Rabbi Kuber goes out of his way to explain, and even justify, opinions with which he himself clearly disagrees. This act of integrity demonstrates true intellectual honesty on Rabbi Kuber’s part and is somewhat of a departure from the more polemical nature of other works written on this controversial topic.

The first volume of Rabbi Kuber’s trilogy offers an overview of the historical circumstances that first led to the question of where to place the halachic dateline. He surveys the various opinions on this question and then carefully considers how a person should treat such places as Japan, Australia, New Zealand, Alaska, and Hawaii.

When all is said and done, this reviewer counted more than 10 different opinions on where the halachic dateline ought to be placed – all of which are thoroughly considered in Crossing the Dateline. Although the nature of Rabbi Kuber’s analysis sometimes borders on the technical and tedious, it remains a gratifying and intellectually-stimulating read.

A large chunk of the first volume of this work is dedicated to elucidating various ways of explaining a somewhat obscure Talmudic passage concerning the sanctification of the new moon. The explanations of the different commentators to that passage bear direct relevance on the question of where the halachic dateline should be.

Rabbi Kuber also presents a fairly lengthy chapter on the opinion of the Radvaz, who would seem to reject the notion of a halachic dateline entirely and instead endorses a “personalized” way of determining the day of the week when in doubt.

In volume II of Crossing the Dateline, Rabbi Kuber focuses on the practical ramifications of the dateline’s existence. He begins with a lengthy study on the halachic consequences of crossing the dateline from, or to, a zone where it’s either Shabbos or yom tov. Can Shabbos, for example, start or end in the middle of a day (instead of at sunset) for a traveler crossing the dateline? Must the same prayers be recited on consecutive days if one lives through a special day twice (once on either side of the dateline)? When should one recite Kiddush if a person crosses the dateline and suddenly finds himself in an area where it’s Shabbos?

Other questions that come up when crossing the dateline into tomorrow or yesterday relate to lighting Chanukah candles, Purim, hilchos niddah, and davening. The second volume actually ends with a 50-page quick reference guide that summarizes the relevant halachos for crossing the dateline.

The third volume of Rabbi Kuber’s magnum opus feature several essays on topics that are somewhat tangential to the book’s core discussion. They are more scientific/technical in nature and concern such topics as molad, bein ha’shmashos, and marking time in outer space.

Rabbi Kuber’s vast halachic knowledge and experience qualifies him to offer his learned opinion on even the most complex topics – and he does not shy away from doing so. Yet, his personal humility shines through from his analysis and conclusions.

This wonderful book touches on all sorts of fields. Obviously, Rabbi Kuber’s discussions involve geography (he makes ample use of Google Maps to reify discussions), but they also include the philosophy of halacha, some lamdus, some astronomy, some mathematics, and even some history (see his discussions of Ptolemy’s map of the inhabited world).

In general, repetitiveness is not usually considered good form, but in a complicated work like Crossing the Dateline, Rabbi Kuber skillfully uses repetitiveness to make sure the reader is still following along as his discussion becoming increasingly more complex.

He is not as meticulous in citing sources as one might expect of a master educator like Rabbi Kuber, but he probably wished to keep the focus on the ideas/arguments rather than on the rabbinic personalities behind them.

The bottom line, though is this: If you were ever interested in the topic of the halachic dateline but did not know where to start, this book is for you. And certainly, if you ever travel to the area between California and China, this book is a must-have.


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Rabbi Reuven Chaim Klein writes The Jewish Press's "Fascinating Explorations in Lashon Hakodesh" column.