A person who believes so strongly in the
apocalypse of 2012, that they totally throw their lives away to whatever thinking that even trying is to no avail towards a happy, "normal" life.
Teenage apocalypticans usually drop out, become assholes towards other people, or just do whatever they please at an attempt to be happy thinking their lives are going to end soon anyway.
But positive apocalypticans usually try to make haste with their "short" lives and try to do good in the world, like
trying to help the
environment, or protest the war, or just try to be a good person altogether.
John tries to be
the best person he could be, he's a
vegetarian, he cares for the
environment, and he's really friendly, and at the same time, Mathew is just sitting in class staring at the ceiling while he waits impatiently for the bell to ring so he can get out and hang with his friends at the mall, both very different, but they're both apocalypticans.