Today, 375 years ago, in the year 1645, a wedding was arranged, at the fair in Gnesen [Gniezno, Poland].
The reason behind this wedding in the days of Sefirah is as follows. The couple to get married was a widow and a widower, and they were supposed to get married on Lag BaOmer, but the widower fell ill. They couldn’t push off the wedding for after Yomtov for various reasons, therefore, Rabbi Chanoch Darshan of Gnesen, allowed this marriage to take place on 21 Iyar, 36th of the Sefirah.
Sources: Chinuch Beis Yehuda, 21.