// ::xum::.org - getWeek() 
//-------------------------------------
// numero de la semaine pour un objet Date

Date.prototype.getWeek = function(){
var a = this.getFullYear(), m = this.getMonth()+1, j = this.getDate();
var S = Math.floor(a/100), A = a%100;
var aB = (a%4==0 && a%100!=0) || (a%1000==0) ? 1: 0;
var jNA = (5*S + Math.floor(S/4) + A + Math.floor(A/4) + aB*6)%7;
var w = Math.floor((jNA+(m==1 ? j: m==2 ? 31+j: Math.floor((30.6*m)-32.3)+j+aB*1)+5)/7)-Math.floor(jNA/5);
return (w==0 || w==53 ? 1: w);
}