Between what two centuries were the Szlachta pirveleges, which formed the cornerstone of the Polish political system, granted?
Szlachta privileges: The privileges of the "szlachta" (Poland's nobility) formed a cornerstone of "Golden Liberty" in the Kingdom of Poland and, later, in the Polish-Lithuanian Commonwealth. Szlachta privileges:  Most of the privileges were granted between the late 14th and early 16th centuries. Golden Liberty: Golden Liberty (Latin: "Aurea Libertas" ; Polish: "Złota Wolność" , Lithuanian: "Auksinė laisvė" ), sometimes referred to as Golden Freedoms, Nobles' Democracy or Nobles' Commonwealth (Polish: "Rzeczpospolita Szlachecka" or "Złota wolność szlachecka", Latin: "aureă lībertās" ) was a unique political system in the Kingdom of Poland and, after the Union of Lublin (1569), in the Polish–Lithuanian Commonwealth.
14th and early 16th centuries