I have seen a custom (it seems to me primarily among Chassidim) to eat matza on 14 Iyar (known as Pesach Sheni). What is the earliest source for this custom? What are the reasons given for following it?
As an aside, I always found this custom odd, as the matza that was eaten with the Korban Pesach Sheni was eaten on the night of 15 Iyar. 14 Iyar is the day on whose afternoon the Korban was offered. Shouldn't the custom be to eat matza on 15 Iyar?