Janko of Czarnków, chronicler and Deputy Chancellor, was born around 1320 to a Czarnków village mayor’s family. He studied at an Italian university and started his ecclesiastical career in Mecklenburg and in the Polish town of Tarnów. In 1356, he was made Canon of Poznań and Gniezno; in 1362–1366, he was sent envoy to Avignon.

Enjoying support from King Casimir the Great (1333–1370), he was promoted to Deputy Chancellor royal and in 1367 was appointed Archdeacon of Gniezno. A year after the King died (1371), he was accused of having stolen the royal insignia and condemned to loss of property and banished. Having left Poland, Janko sojourned in Prague, among other places.

As his exile was eventually cancelled, Janko returned to his native Poland in 1374 and settled down in Gniezno, regaining his once-lost Archdeaconate. After 1382, he was made administrator of the archbishop’s estate. In those years, he busied himself gathering historical materials and writing his Chronicle that encompassed the period of 1370 to 1384; the work has become one of the most interesting monuments of Polish historiography. Janko died in Gniezno in 1387.