Yes, the dates will be changing. You're welcome to choose any dates you'd like for the mission, provided that Zelos and Reim aren't down there on Oros beyond January 31st.

We're sorry for the date confusion and also that we didn't catch it when we were responding to your Gamma mission reporting comment to provide this information then. Now that we have a better idea on how to pace the events going forward, this error won't happen again, but we understand that it's an inconvenience right now. So please choose whatever dates fit your plans for your characters in the game.