FF calendar change XML ff_calendar_thisweek.xml

Since FF has change its download server to : https://cdn-nfs.forexfactory.net/ff_...r_thisweek.xml
I encountered a curious problem

If I write https://cdn-nfs.forexfactory.net/ff_...r_thisweek.xml in Internet explorer I get the right week from 5.3 to 12.3

if my script use
string lURL="https://cdn-nfs.forexfactory.net/ff_calendar_thisweek.xml"; //avant 3/3/17 -> "http://www.forexfactory.com/ffcal_week_this.xml";
and
res=WebRequest("GET",lURL,cookie,NULL,timeout,post,0,result,headers);

it download the previous week from 26.2 to 3.3 ? it seems to read it from a cache !

any ideas ?

thanks

Phil