No, Seam doesn't have anything built in to help you here. You'd have to manually deconstruct and reconstruct the date from the form fields.
I put a component together once to make this sort of thing easier; email me if you're interested in the code. It's a little large to post here, I think.
Hi Matt, that'd be great if you could send me that code you made. I couldn't find your email address, would you be ale to email me at veerukrishnan hotmail com?
Thanks so much.
Just sent it.
(I didn't realize my email wasn't available from my profile page here; oh well)