To listen to some people's theology, you would think that Jesus was crucified on the Day of Atonement, but he wasn't. Think about that for a minute. Passover is about freedom from bondage. The Day of Atonement is about covering up the past. Passover is about the future.
Yes, Christ's death and resurrection accomplished atonement; scripture is clear about that, although the mechanics aren't. But, the fact that Jesus was crucified on Passover sends us a clear message that we are free!