hi,
i got 1970/01/01 when i was trying to set NULL date (for example $date1='' or $date1 is NULL):
$("#date1").datePicker().dpSetSelected('<?$date1?>');

because i havent found another solution, i have changed dpsetselected function to get real NULL date back:
dpSetSelected : function(d, v, m, e)
        {   
            if (d == '') d=null;
            if (v == undefined) v=true;
            if (m == undefined) m=true;
            if (e == undefined) e=true;
            return _w.call(this, 'setSelected', Date.fromString(d), v, m, e);
        },

please let me know if there is another way.
thanks.