Date field open as a calendar

Yeah, I don’t know about compatible plugins for that, but it’s possible. This is a Javascript thing, so if the plugin could be set up to trigger on the specific field (using a CSS selector in the jQuery style), it would work.

If there’s no plugin, the way to do this is (well, you’ll have to know your Javascript pretty good…) is to create a custom template and put the javascript there. There are several Javascript calendar pop-up scripts out there. I strongly suggest you use one that uses jQuery.