I reached the credits with all artifacts except for two of the final ones. Yet even though it looked like this should be locked behind all of them, I was able to access the night warp. I used it and was sent back to the beginning of the credits with no visible change. Then I went through the credits, yet it's still daytime. Was the night warp supposed to fail because I don't have all artifacts or is this some sort of bug?

Edit: I should note that after using the shift, I did revisit its location just to see if the sign changed (it didn't). But I didn't use it a second time.

Edit 2: I'm forced to conclude that I can't get the night shift to work. I got all artifacts now, yet it still does nothing. I'll have to put my playthrough on hold until someone can explain how it works.

Edit 3: Okay, I figured it out. So using the shift there doesn't actually switch between day and night like I assumed. It just unlocks the ability to use the bed to do that. I don't think this was explained very well. But I guess I can keep playing now. Still don't know if I was supposed to be able to access the shift without all artifacts, though.

Edit 4: Another glance at the editor made it clear that I was indeed not supposed to be able to access the shift without all the artifacts. I was missing two from the Sky Temple.