If not a bug, this is a bad behavior. I think all dimensions are supposed to be in synch, except The Nether and The End, where the flow of the time is disregarded (the clock item goes crazy, see http://minecraft.gamepedia.com/Clock#Usage), thus players are not required to go to bed to skip the nighttime.On our little server with only a few people on we discovered that it is easy to get the moon day night cycle out of sync with the Overworld.
People on the Overworld sleep to advance to dawn, while there is someone on the moon... poof things are out of sync.
This is not a complaint nor do we consider it a bug nor asking for anything to be fixed
In what version of Galacticraft this happens?