Why are the Dates of Purim Celebrations dependent on the Location?

Purim is different from all other Jewish holidays in at least one very interesting aspect. Purim is observed in some places exclusively on the 14th of Adar and in others, exclusively on the 15th (Shushan Purim). The specific day on which Purim is celebrated depends on the localtion; in places where Purim is celebrated on the fourteenth, it is not celebrated on the fifteenth and vice versa.

The original observance of Purim as a festival was established by the Sages and the Prophets who decreed that it be observed in every generation, as we read in the Megillah: To establish these days of Purim at their appropriate time (9:31). They explained: "these days…. at their appropriate time", i.e., the time appropriate for one [city] is not appropriate for the other [city].

Why were different days established as Purim in different cities? Why wasn't one day chosen as Purim in all cities, just as other festivals are celebrated on the same day in every city?

We find that even in the times of Mordechai and Esther, Purim was celebrated on a different day in Shushan than in the other cities. In all other cities, the battle took place on the thirteenth of Adar and the people rested and celebrated on the fourteenth of Adar. In Shushan however, the battle took place on the thirteenth and fourteenth of Adar and the people rested and celebrated only on the fifteenth.

It was therefore proper that only the city of Shushan should celebrate on the fifteenth of Adar, for it was only there that Purim was celebrated on that day. The Sages of that era, however, wished to accord honor to Jerusalem and to the Land of Israel which was desolate at the time.

They therefore issued the following ruling: Shushan ? where the miracle occurred ? has an importance of its own and celebrates Purim on the fifteenth, even though it was not settled and thus did not have a surrounding wall at the time of Yehoshua bin Nun (Joshua). Other cities which were settled and had walls at the time of Yehoshua bin Nun, even if they are in a state of ruin and are no longer surrounded by walls, are considered to be important. They are therefore accorded the status of Shushan and celebrate Purim on the fifteenth. Cities which did not have surrounding walls at the time of Yehoshua bin Nun ? even if they have walls surrounding them today ? are to celebrate Purim on the fourteenth of Adar.

The criteria for judging whether a city is given the status of Shushan or not ?regarding celebrating Purim on the fifteenth rather than the fourteenth ? is thus linked to the state of that city at the time of Yehoshua bin Nun. Its present state is not taken into account; i.e., even if the cities in the Land of Israel were desolate at the time that Purim was established, the fact that they were settled and surrounded by walls when Yehoshua bin Nun conquered the Land of Israel gives them an importance which makes them equivalent to Shushan. Their present state of destruction [i.e., at the time when the Sages established Purim] is considered to be temporary.

As regards cities outside the Land of Israel: Even though they may be considered important and may be surrounded by walls today, since they were not important at the time of Yehoshua bin Nun, they are not given the status of Shushan, and Purim is celebrated on the fourteenth.

Hence, the Purim which is celebrated on the fourteenth of Adar is referred to as Purim of the "open" [i.e., unwalled, or less important] cities, whereas the Purim which is celebrated on the fifteenth is referred to as Purim of the walled (major cities).

Today, the only city in which Purim is celebrated on the fifteenth of Adar ? besides Shushan ? is Jerusalem. Although the Me illah is also read on the fifteenth of Adar in a number of other cities in the Land of Israel: Acre, Jaffa, and Tiberias, this is only a custom based on the possibility that they may have been surrounded by walls at the time of Joshua. These cities celebrate Purim on the fourteenth; the additional Megillah reading on the fifteenth is a stringency based on doubt as to their status and thus, they do not recite the blessings when reading on the fifteenth.