Tiḳun Tu Bishevat

A Tu BiShvat seder is a festive ceremony, often accompanied by a meal featuring fruits in honor of the Jewish holiday of Tu BiShvat. During the Middle Ages or possibly a little before that, this day started to be celebrated with a minor ceremony of eating fruits, since the Mishnah called it "Rosh Hashanah" ("New Year"), and that was later understood as being a time appropriate for celebration.