If you're using jQuery's built-in dialog box plug-in and you want to add a Datepicker field to a dialog box, you'll notice that the Datepicker opens behind the dialog box by default.

A quick and easy solution to force the Datepicker to appear in front of the dialog box is to give the Datepicker a really high z-index.

Just add this to your CSS file:

#ui-datepicker-div {
    z-index: 10000;
}