You have to enter the Batallia, Sauromugue, or Rolanberry ones first. Whichever portal you come back from is the only one you can use. IE, enter Batallia's maw, you get dumped into Sauromugue, but you end up coming back through the Rolanberry one. At that point, you can only use the Rolanberry one to go back to the past. Once in the past, you can use any maw you come across, and it will allow you to use it in present time, too. So anytime you see a maw in the past, use it, then use it again in the future and to go back in time again and keep on treking.