Traditionally, Ryan was an Irish name, but who knows today?
Unless he is retarded, a 12-year-old already has a clear sense of the calendar. I think it would be too late for his father to teach him a different definition of "years".
I have four children, ages 11, 9, 8, and 4. My oldest three are all very bright and have tested high to gifted ranges in intelligence. The 4 year old hasn't been tested, but this morning, she downloaded a movie from Netflix onto our Galaxy tablet.... so I'm guessing she's not too shabby in the brains department, either. lol
However, if I tell them Saturday is Sunday, they will most likely believe it. They may figure it out when they go to school, and it's Monday, but if they didn't go to school, they would believe whatever I told them because they trust me. I could see to where my 11 year old could get the years mixed up.
Also, we know they were "living in the woods," but does that mean they never came out? For all we know, these people could have been making regular trips into towns for supplies, food, possibly even haircuts, but still going back out to the woods. The father could have had a mental condition that made him paranoid/fearful of the public/government/family/etc and they choose to live there. My children would live with me in the woods if I told them to, and told them that someone in "town" would harm them. They love their father and I, and would not run away to be "saved" in town if they had been brainwashed that people were dangerous. If he knows his name, I don't guess there's much mystery at all. They'll soon release the information they know.