If you’ve been in Israel over Passover or Sukkot you’ve definitely noticed the phenomenon: While the holiday might be over in Israel, for others – the Jews of the Diaspora – it continues. Israelis line up outside bakeries, sit in coffee shops and spread cream cheese on their bagels, but for the Jews of the world, unleavened bread is still the rule of law.The same happened over Sukkot this past week. In Israel the holiday ended on Monday. But for the rest of the Jewish world, it continued for an extra day, until nightfall on Tuesday.The reason Jews in the Diaspora keep an extra day for Sukkot, Passover and Shavuot is because of the way a new month used to be set by the Sanhedrin, the ancient Jewish judicial assembly. At the time, witnesses needed to see a new moon in Jerusalem. Only then, after it was confirmed, would bonfires be lit or messengers dispatched so neighboring Jewish communities – outside the Land of Israel – would know that a new Jewish month had begun.Since there was always uncertainty in Jewish communities outside Israel about when the new month started – Was the bonfire accurate? Did the messenger arrive on time? – a second day was added to each festival to ensure that at least on the real day, whichever it was, the holiday was observed.The extra day was not being kept because God had ordered; it was being observed so Jews could do their best to ensure that they were doing what they believed God wanted.This means that if our forefathers only had telephones, email accounts or airplanes, a second day would have likely never been added. But they were, and became part of the halachic (Jewish law) codex that has been continuously observed even after the Jewish calendar was fixed by Rabbi Hillel II in the 4th century.So why, 1,600 years later, do most organized Jewish communities throughout the Diaspora – all Orthodox and most Conservative – continue to observe a day that everyone knows is not really part of the biblically mandated holiday? With the calendar now calculable and known in advance, why is this extra day still needed?I’ve been thinking about Yom Tov Sheni – the halachic term for these extra days – after spending Sukkot in the United States, and watching all different types of Jews keep an eight-day holiday while my family kept the seven days in line with the way it is observed in Israel. It struck me that while it might seem on the surface to be only a discussion about a few extra days of holiday each year, what we might really be talking about is the definition of a nation, as well as a possible symptom for the much-hyped divide between the State of Israel and Diaspora Jewry.The reason this issue is of interest for me is because for the first time in over approximately 2,000 years, Israel is home to more Jews – about 6.6 million – than anywhere else in the world. Israeli-Jews constitute almost 45% of the entire Jewish population worldwide. This is relevant because as long as it seemed that most Jews lived in the Diaspora – something that was the case until a few years ago when there were more Jews in the United States than in Israel – there was an argument to be made for continuing to adhere to age-old customs made for a people in exile.But Jews are no longer in exile. For the first time since the Babylonian exile, we have more Jews in Israel than anywhere else in the world, an historic game-changer that should have significance on a national and religious level for the Jewish people.Some readers might wonder why this is even important: Let different communities adhere to different customs, they might argue. Why change something that has been done the same way for 17 centuries?The reason is because in this small detail, we see a microcosm that partially explains the ongoing – and growing – divide between the Jews of Israel and the Jews of the Diaspora. Jews are born all across the world and do not share citizenship. There are Jews in Spain, in France, in South Africa and in Israel. They carry different passports and grow up speaking different languages.What they do have in common, though, is the use of the Hebrew language at home, in school and in prayer. They share the same Jewish symbols (apples and honey, etrog, menorah, etc.) as well as what should be the same calendar. When 6.6 million Jews in Israel are eating bread and the rest of the Jewish communities around the world are still eating matzah, there’s something wrong.Sharing the same calendar creates a sense of solidarity and unity between Jews around the world. Does it solve the problems that exist at the Kotel, where there still is not a respectful place of prayer for progressive Jews? No. Does it solve the problems caused by the Orthodox monopoly over conversion in Israel? Of course not. But it does create more of a shared destiny and purpose. It helps foster national unity.That this has not been changed until now could also reflect one of the reasons why the above-mentioned problems continue to cause strife among Jews worldwide. To change something in Jewish law requires courage, especially in the more stringent Orthodox community where change occurs at a crawling pace.Canceling the second day of chag would undoubtedly be controversial, and would not be accepted by all segments of the Jewish Diaspora. But it would bring with it the upside of helping bridge what some believe is a divide that cannot be joined. It could be an important step in showing that Jewish life evolves and adapts.I can imagine that some readers are probably thinking: Only rabbis should be allowed to voice an opinion on Jewish law, and that canceling the eighth day of Sukkot and Passover falls into that category. But this carries with it more than just religious significance – this is about the identity of a nation, as well as the kind of people Jews want to be today when the State of Israel serve as home to the world’s largest Jewish community.Later this month, the Jewish Federations of North America will convene in Tel Aviv and Jerusalem for the annual General Assembly. The slogan for this year’s gathering is “We need to talk.” We do. If we want to remain a united people, then unity needs to be an important goal and ambition. One small step in that direction would be syncing our calendars.