There's no planet named "galaxy" in our solar system or in any cataloged extrasolar planets.
To determine the length of a planet's day (its rotation period), you would need information about its:
* Mass: A more massive planet will have a stronger gravitational pull, potentially influencing its rotation speed.
* Composition: The density and internal structure of a planet affect its moment of inertia, influencing how quickly it spins.
* Orbital dynamics: Interactions with a star or other celestial bodies can affect a planet's rotation over time.
If you're creating a fictional world, you can choose the length of day you desire for the planet "galaxy." There are no limitations, and it can be as long or as short as your story demands.
