According to the folk calendar - Peter and Pavel Ryabinnik

This day is associated with the names of the Christian saints Peter and Paul. September 23 was sometimes called the name day of the mountain ash. On this day, it was customary for people to collect its fruits, leaving a little on the tree as a treat for the birds. New beginnings and travels were planned for Ryabinka. There was a belief that a business started on this day would definitely end well.