This year's Purim is unique. Shushan Purim which is the 15th of Adar comes out on Shabbos. Our Rabbis were afraid someone might mistakenly carry the Megillah on Shabbos in a public thoroughfare (which is prohibited), and decreed that the Megillah not be read on Shabbos, but on Thursday night/Friday like the rest of the world.
There is a Gemorrah Yerushalmi that states that the festive meal of Purim should be separate from the Shabbos meal and therefore those who celebrate Shushan Purim (namely Yerushalayim) have their festive meal on Sunday. The Mitzvah of Shaloch Manos is connected to the festive meal and is therefore also performed on Sunday. Matanos L'evynim (for the poor) is connected to the reading of the Megillah and is done on Friday.
On Shabbos, since it is the actual Shushan Purim , the Al Hanisim prayer is said and the laws of Purim should be discussed.
Lastly, some Rabbs disagree with the above and are of the opinion that a festive Purim meal doesn't conflict with Shabbos, but in deference to the other views one should have a festive meal both on Shabbos and Sunday. Thus, Purim meshulash, i.e. triple Purim.
I'll drink to that!
Freilich Purim.- Thank-you once again Rabbi Glazer.
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