quinquagesimal
/ˌkwɪŋkwəˈdʒɛsɪml/adjective
Designating, belonging to, or relating to a set of fifty things (especially days); based on division into fifty parts.
Origin
Mid 17th century; earliest use found in Daniel Cawdrey (d. 1664), Church of England clergyman and ejected minister. From post-classical Latin quinquagesimus fiftieth + -al.