How long does it take to animate?

Hello everyone, I’m not very knowledgeable of animation so forgive me if this question is insane or another how long is a piece of string.

Lets assume you wanted to make a 3D show. A full season of 12 30min episodes you would release weekly. All the art is finished, characters, weapons, environments, rigging, etc. How long would it take to animate? (Assuming render time is not a factor)

I know there are other factors so I’ll try to narrow it down. The episodes would have maybe 1 - 5 “main” characters on-screen in any one moment, in one environment for the episodes duration. How fast could this be done by one person, assuming (s)he just had to animate?

I was thinking of something like this…

Of course it wouldn’t be that detailed. The background characters would be black silhouettes but besides that i would like the characters and environment to be fairly beautiful. I heard about a process called tweening that seems like it would make animation a pretty easy thing to do. So, can this be done within, say, a year?