Blast to the past

When the Flock's go-kart spins out of control and crashes, Mossy Bottom Farm has changed. The Farmer is much younger, the pigs are wearing nappies, and the cockerel is just a baby. It's clear to Shaun the Sheep that Bitzer and the Flock have travelled back in time! The young Farmer doesn't know much about farming, and the farm is a mess. Can the animals teach the Farmer his job and then find a way to return to their own time?