In the Roman Catholic tradition, October 4 is the Feast of St. Francis of Assisi.
St. Francis (1182-1226) was a monk who founded the contemporary order of Franciscans. He was known for his vow of poverty and his special connection to animals, among many other things.
Many Unitarian Universalists have picked up on the Catholic tradition of blessing animals, particularly pets, on this day. St. Francis may receive little attention at this service, but a number of congregations will bless pets at the service. Some people bring their pets to church, others bring photographs of their pets; others have their pets blessed by naming them.
You can learn more at this UUA link: https://www.uua.org/worship/holidays/animal-blessing