When is Catherines birthday in the book Catherine Called Birdy?

In "Catherine, Called Birdy" by Karen Cushman, Catherine's birthday is on March 17th. The novel is set in the year 1290, and her birthday is mentioned as a significant detail that highlights her coming-of-age and the challenges she faces in her medieval society. Throughout the book, Catherine reflects on her life and aspirations as she navigates her teenage years.