Can't get valid tickets to Coliseum?

Looking at the Coliseum ticketing website, it "seems" to suggest that any tickets purchased are only good through December 31, 2017. Has anyone bought tickets from their website and confirmed they are good through 2018?

"ticket colosseum, roman forum, palatine and current exhibitions - valid for 2 days the ticket can be used within 31/12/17."

When are you trying to purchase for? They don't sell them very far in advance.

I was looking at April, 2018