[jQuery] Stop datepicker onDayLinkClick refreshing page

[phoebebright]

I have a simple function:

                onDayLinkClick: function(date) {
                    $('#id_from_date').val(date.asString());
                    return false;

It puts the value in the field but then refreshes the page.  Using
Firebug it seems to be somewhere deep in Datepicker.  Is there a way
of stopping this?  Tried return true and does the same thing.