44 Pa. Stat. § 22
The Governor shall annually issue his proclamation designating and calling upon the public schools, other educational institutions of the State, and the citizens of Pennsylvania to observe the birthday of William Penn, the great Founder and Governor of Pennsylvania. Said birthday of William Penn shall be observed on the twenty-fourth day of October of each year, unless such day falls on Saturday or Sunday, in which event the Governor may designate the preceding Friday or the following Monday. In pursuance to said proclamation of the Governor, appropriate exercises with respect to the life of William Penn, the Founder and Proprietor and Governor of Pennsylvania, and the principles advocated by him in founding Pennsylvania, shall be held in the public schools and other educational institutions under the Commonwealth.
44 P.S. § 22