Gaj was formerly part of the German Empire. In the German Empire, the place was called Birkenfeld.
The place is now called Gaj and belongs to Poland.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Gaj | German Empire | Witkowo | before the Versailles Treaty |
| Gaj | Poland | Gniezno | after the Versailles Treaty |
| Birkenfeld | German Empire | Gnesen | 1939 |
| Gaj | Poland | Gniezno | 1945 |
| Gaj | Poland | Konin | 1992 |