I knew it was. I tend to agree that Jesus is bullshit, (actually I am more agnostic about that). Thy hypothesis has often been that the stars weren't aligned correctly, and some of the indicators of what was around in his birth doesn't mesh with December. I can't dig that information, and don't take that seriously until you look that up, but I recall something like that. (I know, bad atheist)
While I think some of Zeitgeist and other works that make similar claims regarding earlier religions and Christianity have some degree of truth, I also believe they play loose with the facts. Much like Michael Moore's films, there is a lot of circumstancial evidence where the facts could be interpretted to be connected, but there is not sufficient evidence to conclude that they are definitively connected. Many of the claims made by Zeitgeist and authors like Acharya S are speculative. Furthermore, these authors tend to cite each other as sources. I would like to see the primary sources where these claims originated.
As I said, there is some amount of truth in these stories, but it is hard to distinguish fact from fiction.
"The Christian religion is a parody on the worship of the Sun, in which they put a man whom they call Christ, in the place of the Sun, and pay him the same adoration which was originally paid to the Sun." - Thomas Paine