How does space time differ within a galaxy? Not the same question but is similar to other marked duplicate. 
How much time dilation  does the center of a galaxy can exist and sustain human life from our point of view? What would a day equal to each others point of view looking at each other?

I'm not asking about moving celestial bodies moving from each other but the difference in the gravity wells from the center of our galaxy being generally denser then the edge of a galaxy.





This is another way of asking if I wasn't clear above the line. Not to invalidate any answers.

Point 1 being near the center of the galaxy and point 2 at the the most edge the galaxy. How much would the differences in the galaxies gravity well point 1 being deeper in the center compared to the point 2 the edge effect time?
The gravitational redshift factor and also the factor by which time dilation occurs in a gravitational field is approximately $GM/Rc^2$. Here, $R$ would be the radius from which light was emitted and $M$ is the amount of mass within radius $R$ (making the crude assumption of spherical symmetry).

Thus, for an external observer,  light emitted from a radius of 10 kpc, might have $M \sim 10^{11} M_{\odot}$ in the galaxy shown. The redshift/time dilation factor is only $5\times 10^{-7}$ and is basically negligible.

This could perhaps gets an order of magnitude bigger as one approaches the denser central bulge, but is still very small.

The only appreciable redshift and time dilation effects will come in the immediate surroundings of any supermassive black hole. By immediate, I mean within about a hundred Schwarzschild radii, where $R_s = 2GM/c^2$. In our Galaxy that would mean within a billion kilometres.