Дата в формате dd.mm.YYYY

var d = new Date(); // текущая дата
var x = 1; // смещение
var y = (d.setDate(d.getDate() - x));
document.writeln("Дата равна: " + y);

function OnInsertFormValidate (fieldVAlues, errorInfo)
var date_start = new Date();
var date_end = new Date();
var days_start = 2;
var days_end = 4;
  
date_start.setTime(date_start.getTime() - (days_start * (1000 * 60 * 60 * 24)));
today_start =  date_start.getDate() + "." + ( date_start.getMonth() + 1 ) + "." + date_start.getFullYear();
    
date_end.setTime(date_end.getTime() + (days_end * (1000 * 60 * 60 * 24)));
today_end =  date_end.getDate() + "." + ( date_end.getMonth() + 1 ) + "." + date_end.getFullYear();
 
if ((fieldValues['DATE_OPERATIONS'] < (today_start)) || (fieldValues['DATE_OPERATIONS'] > (today_end)))
{
    errorInfo.SetMessage('Дата указана в неверном диапазоне'); 
    return false;
}
}

var s = -2,
    e =  4;
 
function f (x) {return ((x < 10 ? '0' : '') + x)}
 
var d = new Date ();
 
d.setDate (d.getDate () + s);
   var sDt = [f (d.getDate ()), f (d.getMonth () + 1), d.getFullYear ()].join ('.');
 
d.setDate (d.getDate () + e - s);
   var eDt = [f (d.getDate ()), f (d.getMonth () + 1), d.getFullYear ()].join ('.');
 
alert (sDt + ' -- ' + eDt);