Most people love the joyful, often frenetic one-day holiday of Purim. When, like this year, it falls on Friday, segueing into Shabbat, it’s even more frenetic than usual—no more delaying the seuda till evening, or lingering over dessert.

But in Israel, it’s even more complicated than that because Shushan Purim— celebrated on 15 Adar (rather than the 14th), in Jerusalem (and other cities that were walled at the time of Yehoshua)—falls on Shabbat itself, when it cannot be appropriately celebrated. In such a case, Purim is celebrated over three days instead of one and is appropriately called Purim Meshulash.

The fact that 14 Adar never falls on Shabbat avoids this problem for most Jews. But Shushan Purim occasionally does coincide with Shabbat, occurring at a minimum interval of three years and a maximum interval of 20. (The next one is in 2045.)

The festivities are then thus divided: The Megillah reading and distribution of charity take place on Friday (Adar 14), which is called Purim Deprazim (without a wall). Al Hanissim is recited only on Shabbat (Adar 15), which is Shushan Purim itself. The weekly parsha is read as usual, while the parsha for Purim is read for Maftir, and the Haftarah is the same as read the previous Shabbat, Parshat Zachor. On Sunday (Adar 16), mishloach manot are sent and the festive Purim meal is held.

Due to doubt as to whether other cities were sufficiently walled in Yehoshua’s era, it is customary in certain towns (including Hevron, Tzfat, Tveriah, Acco, Ashdod, Beersheva, Beit She’an, Beit Shemesh, Gaza, Haifa, Yaffo, Lod, Ramlah and Shechem) to celebrate Purim on the 14th and hold an additional Megillah reading on the 15th without reciting the blessings. The same holds true in the Diaspora for cities such as Tyre, Sidon, Damascus, Izmir, Baghdad and Prague. This is relevant for soldiers in the IDF who might, unfortunately, find themselves in some of these locations.

The only city that currently celebrates only Shushan Purim is Jerusalem; however, Rabbi Yoel Elizur has written that residents of Beit El and Mevo Horon should observe only the 15th, like Jerusalem. And residents of those cities may also duplicate the other mitzvot of the previous day. Why not more gifts and feasts when in doubt!

What happens if Mashiach comes sometime during Purim? The festivities continue, because Purim is one of the holidays that will continue into perpetuity, according to Halacha: “And these days of Purim shall never cease among the Jews, nor shall their remembrance perish from their descendants.” (Megillat Esther 9:28)

But where would Mashiach celebrate Purim? That depends on several factors such as when and where he arrives (Jerusalem, of course!) and where he plans to sleep.

Since most people have family in different cities, people who live in Jerusalem can celebrate regular Purim (Adar 14, this year on Friday) with family and friends in other cities, making sure to be home in time for their Megillah reading, whereas people who, for example, live in the center, will go to celebrate Shushan Purim in Jerusalem (this year postponed to Sunday, Adar 16). And that’s all good. But it’s best to check the halachot and how they apply if your Purim is celebrated over several cities.

One of the adjustments that Israeli teachers or other kinds of shlichim have to make is celebrating Purim on the 14th if they are from Jerusalem.

In Israel, most kindergarteners and kids in the younger grades wear their Purim costumes to school on Rosh Chodesh Adar, something that always brings me to tears, and their parents to their cameras. Also, it’s quite normal to see both kids and adults in costume at various points throughout the first two weeks of Adar, as many workplaces suspend their dress codes until Purim. In other words, don’t be surprised or alarmed if a gorilla gets on your bus.

Purim is always a festive, and often a manic, time no matter where you celebrate it. Allow me to end with a nice story I heard from Moshe Mandel:

One time in the Jerusalem neighborhood of Nachlaot (known for its artistic, and colorful,residents) when there was a Purim Meshulash, the children decided to have a special type of costume competition. For each of the three days, the costumes had to be different and each day was devoted to a specific theme: On Friday, the costume was on the theme of nature. On Shabbat, the costume was on the theme of history, and on Sunday, the costume was on the theme of fictional characters. The entire neighborhood participated, and the streets were full of colors and stories which created a magical and especially festive atmosphere!

Wherever you celebrate this year, Purim Sameach! And may we all soon be united in celebration in Jerusalem!

Rosally Saltsman is a freelance writer, originally from Montreal, who lives in Israel. Come join her!