We are given no precise sense of how much time has passed in this play in between Act One and Act Two, yet I think we can safely infer that roughly a month has passed. In Act One, we are introduced to a Nora who has been buying presents and decorations for Christmas, such as the tree, and who eagerly asks her maid to hide the tree for her so that the children will not see it until it is decorated. In Act Two, Nora begins by giving us a firm time marker:
There's someone coming! No, it's no one. of course - no one'll come today. It's Christmas Day.
So I think we can safely say that the separation between the Acts is roughly a month as this is the normal time between when the majority of people put up their Christmas decorations and celebrate Christmas.