[PunK_HS]

Ответ:

var start = -4,  // Дата начала периода
    end =  4;    // Дата окончания периода
 
function f (x) {return ((x < 10 ? '0' : '') + x)} 
var d = new Date ();
d.setDate (d.getDate () + start);
   var start_date = [f (d.getDate ()), f (d.getMonth () + 1), d.getFullYear ()].join ('.');
 
d.setDate (d.getDate () + end - start);
   var end_date = [f (d.getDate ()), f (d.getMonth () + 1), d.getFullYear ()].join ('.');
 
if ((fieldValues['DATE_OPERATIONS'] < (start_date)) || (fieldValues['DATE_OPERATIONS'] > (end_date)))
{
    errorInfo.SetMessage('Дата указана в неверном диапазоне!'); 
    return false;
}