What's the last thing you did? I'm guessing you just got Robo and wound up at the End of Time. You need to go to Medina Village in 1,000 A.D. to progress in the story. If not, give us more information to work with.
spoi;ers:- - -- - - --- Your still not required to go their.
After beating Heckran jump into the 600 AD portal > talk to the Captain of the Guards at Zenon Bridge > talk to the Cook at the basement of Guardia Castle then go back to Zenon Bridge to continue on with the game.
If the 600 AD portal doesn't appear at the end of time enter the portal right next to Lucca's telepod machine at the top of Leene Square.