Following the talmudic injunction that one must recite a special thanksgiving benediction on returning to the place where one was once miraculously saved from danger (Ber. 54a), the custom evolved for Jewish communities or families to celebrate the anniversary of their escape from destruction by reciting special prayers and with a ritual similar to that of Purim. (See: A. Gumbiner's note to Sh. Ar., OḤ 686.) These special communal Purims are called *Purim Katan ("minor Purim"), or Mo'ed Katan ("minor holiday") or Purim… (followed by the name of the community or the special event). In many cases special Purims were preceded by a fast comparable to the Fast of *Esther. In addition, on the Purim Katan itself the story of the personal or communal salvation was often read from a scroll (*megillah) in the course of a synagogue service in which special prayers of thanksgiving, in the style of piyyutim, were offered. Sometimes the *Al ha-Nissim prayer and the *Hallel were inserted into the ritual. The traditional Purim observances of enjoying a festive meal and giving charity to the poor were also applied to special Purims. (See Table: List of Special Purims.)
The Karaites observe a special Purim on 1st Shevat, in memory of the release from prison of one of their leaders, Yerushalmi. The exact date of the event is unknown. The followers of Shabbetai Ẓevi observed a special Purim on 15th Kislev, because on this day in 1648 Shabbetai Ẓevi proclaimed himself Messiah.
C. Roth, in: HUCA, 10 (1935), 451–82; 12–13 (1937–1938), 697–99; Y.T. Lewinski (ed.), Sefer ha-Mo'adim, 6 (1956), 297–321; M. Steinschneider, in: MGWJ, 47 (1901–21) ff.; A. Danon, in: REJ, 54 (1907).