Most likely it's day if you reffering to the den where beta is. As far as I know to the second part of of the den you can go only in night. First, where there are wolves during the day is open all the time. Is the what you were asking?
I think another requirement is Logan has to be Top/Normal (Green Path). If you sent Logan to the Bandit Camp (Red Path) I think the Black Wolf event is locked. This is why I have two different save files for Logan lol.
