Liturgy of the Hours Question. . .

Ok, so I pray morning and evening prayer using "Christian Prayer: The Liturgy of the Hours." I've only been doing this for just over a year now and so when odd situations come up, sometimes I get confused. For instance last night. Last night I didn't know where to turn. And this morning. This morning do I pray the morning prayer for Dec. 24th or for Sunday Week IV with the Advent antiphons? I'm just slightly confused. If this post makes no sense, then just ignore it. If you can give me some clarification, that'd be helpful. This is kind of an after the fact question, but I'm just curious.