码：

var date = new Date('2011', '01', '02');

alert('the original date is ' + date);

var newdate = new Date(date);



newdate.setDate(newdate.getDate() - 7); // minus the date



var nd = new Date(newdate);

alert('the new date is ' + nd);

使用Datepicker：

$("#in").datepicker({
    minDate: 0,
    onSelect: function(dateText, inst) {
       var actualDate = new Date(dateText);
       var newDate = new Date(actualDate.getFullYear(), actualDate.getMonth(), actualDate.getDate()+1);
        $('#out').datepicker('option', 'minDate', newDate );
    }
});

$("#out").datepicker();​

可能会派上用场的其他东西：

getDate()   Returns the day of the month (from 1-31)
getDay()    Returns the day of the week (from 0-6)
getFullYear()   Returns the year (four digits)
getHours()  Returns the hour (from 0-23)
getMilliseconds()   Returns the milliseconds (from 0-999)
getMinutes()    Returns the minutes (from 0-59)
getMonth()  Returns the month (from 0-11)
getSeconds()    Returns the seconds (from 0-59)