Yud Aleph Nissan, the 11th day of the month of Nisan in the Hebrew calendar (Hebrew: י"א ניסן) is the birthday of Rabbi Menachem Mendel Schneerson (1902-1994), the leader of the Chabad dynasty of Hasidism, and is celebrated by his followers as a festival.
The day had been marked by public parades and sharing with fellows since 1992, when the Rebbe, Rabbi Schneerson, was in hospital recovering from a stroke.
The first public recognition of Rabbi Schneerson's birthday was instigated by his personal envoy to Washington DC, Abraham Shemtov, who urged friendly congressmen to persuade Jimmy Carter to declare the day to be Education and Sharing Day in his honor, in 1978. The day has been declared Education and Sharing Day by all succeeding U.S. Presidents.
The day is marked with many Mitzvah Tank Parades around the world and with an annual official Tzivos Hashem rally, particularly in Crown Heights