Jarnostów was formerly part of the German Empire. In the German Empire, the place was called Ernstdorf.
The place is now called Jarnostów and belongs to Poland.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Ernsdorf | German Empire | Groß-Wartenberg | before the Versailles Treaty |
| Jarnostów | Poland | Ostrów Wielkopolski | after the Versailles Treaty |
| Ernstdorf | German Empire | Ostrowo | 1939 |
| Jarnostów | Poland | Ostrów Wielkopolski | 1945 |
| Jarnostów | Poland | Kalisz | 1992 |