There will be a farbrengen in honor of Pesach Sheni this Wednesday night, May 14, following the 9:30 PM maariv minyan at Tzemach Tzedek.
A year after the Exodus, Hashem instructed the Jewish people to bring the Pesach offering on the afternoon of Nissan 14, and to eat it that evening, roasted over the fire, together with matzah and bitter herbs, as they had done on the previous year just before they left Egypt.
"There were, however, certain persons who had become ritually impure through contact with a dead body, and could not, therefore, prepare the Passover offering on that day. They approached Moses and Aaron ... and they said: '...Why should we be deprived, and not be able to present G-d's offering in its time, amongst the children of Israel?'" (Numbers 9).
In response to their plea, G-d established the 14th of Iyar as a "second Passover" (pesach sheini) for anyone who was unable to bring the offering on its appointed time in the previous month. The day thus represents the "second chance" achieved by teshuvah the power of repentance and "return."
In the words of Rabbi Yosef Yitzchak of Lubavitch, "The Second Passover means that it's never a 'lost case.'"