Is Halloween the new Thanksgiving?

I'm really trying to understand this whole holiday thing. The day before Halloween, there were no Christmas decorations in the stores. The day after, there were Christmas trees, lights, and holiday commercials on both TV and the radio. Did I miss the memo? Is Halloween the new Thanksgiving? Should I be doing my Christmas shopping already? It seems a bit ridiculous to me. We've seemed to have skipped Thanksgiving and fall entirely and jumped straight to winter. I can't even imagine how sick I am going to be of the holiday commercials by the time Christmas rolls around.