It's impossible to tell how old he is. Where did you get him? A breeder will give you the hatch date. He looks young, snakes grow as they eat. If you where to feed him every 2-3 days he could be close to adult size in a couple years, he will also be very fat and have health problems. If he was fed every 10-14 days he could stay this small for a long long time and be skinny and very malnurished. He is probley a 2011 hatchling, no way of knowing when he was hatched without info from the breeder.