Get a breathtaking novel, cross out everything except the chapter headlines, write a complete new story, add some Actors who really don't get the characters right (and really don't have the chance, because the story and their character were crucially changed by the director) and - voilĂ  - you've got Timeline.

I have never seen a movie that completely disregards all information about medieval times the author has given and shows no respect to his work, until now.

Save your time, buy the book and enjoy it.

Spoiler: The only thing I enjoyed was the night shooting of the tribuchets: but even this had it's flaws. I know from personal experience that the sound of tribuchets firing is very different - and I listened to it on more than once on different occasions.