One of the greatest accomplishments of Einstein was to show that the concept of time is "relative", meaning that in different part of the universe, time may flow differently. Based on the General Relativity, an observer in strong gravitational field would experience slower time flow. This effect is very weak on Earth because the gravitational field on Earth is not strong enough. But around a neutron star this would be a very important effect. So in a galaxy, "time" depends on where you are.

Time passes at slightly different rates depending on where you are in the galaxy, but these differences are negligible as far as our experiences are concerned. In fact, time passes at a slightly faster rate on the International Space Station than it does on Earth. This is because of general relativity: the deeper you are in a gravitational well, the slower time passes relative to the outside universe.