Solar System Simulation Software?

[McC]

Are there any applications out there that allow you to, essentially, create a solar system, with different masses/types of stars (one or more), planets, and so forth and then test their stability over the eons?

[General Zod]

Yes.

[Stark]

Is there one that lets you model Sol system planetary positions by date?

[McC]

That's the right idea, but it's a lot more limited than what I'm after. I'd like to see stuff like radiation output, habitability bands, and support for numerous bodies rather than just four.

[Bounty]

Is there one that lets you model Sol system planetary positions by date?

http://www.shatters.net/celestia/

It had a date feature last time I checked.