The Milky Way galaxy, like many spiral galaxies, does not rotate as a solid object with a fixed rotational period. Instead, its rotation is differential, meaning different parts of the galaxy rotate at different speeds.
The Milky Way's rotation is estimated to take approximately 200 to 250 million years to complete one full rotation. This value is often referred to as the galactic year or cosmic year. However, it's important to note that this estimate is subject to some uncertainty, as measuring the exact rotation period of a galaxy is a complex task.
Additionally, the rotation period can vary depending on the specific region of the galaxy being considered. The inner parts of the galaxy, where the concentration of mass is higher, tend to rotate faster than the outer regions.
It's worth mentioning that the Milky Way is a dynamic and evolving system, influenced by various factors such as gravitational interactions with other galaxies, galactic collisions, and the distribution of dark matter. These factors can affect the rotation and structure of the galaxy over long timescales.