Marcin Kromer, was Prince-Bishop of Warmia (Ermland), a Polish cartographer, diplomat and historian in the Kingdom of Poland and later in the Polish-Lithuanian Commonwealth, he was a personal secretary to two Kings of Poland, Sigismund II Augustus and Sigismund I of Poland, of the Jagiellon dynasty, reigned as King of Poland and also as the Grand Duke of Lithuania, during which time span?
Marcin Kromer:  He was a personal secretary to two Kings of Poland, Sigismund I the Old and Sigismund II Augustus. Sigismund I the Old: Sigismund I of Poland (Polish: "Zygmunt I Stary" , Lithuanian: "Žygimantas I Senasis" ; 1 January 1467 – 1 April 1548), of the Jagiellon dynasty, reigned as King of Poland and also as the Grand Duke of Lithuania from 1506 until 1548.
1506 until 1548