calculate number of seconds between two dates

I wrote a JS code that works well on a browser but does not work if i run it from Construct 2.

JS code :

function calc(){

var b = new Date();

var mydate = new Date('Sun Jul 16 2017 11:58:38 GMT+0300 (???? ??? ???????)');

return (b - mydate) / 1000;

}

alert(calc());

on Construct 2 :

Browser.ExecJS("

var b = new Date();

var mydate = new Date('Sun Jul 16 2017 11:58:38 GMT+0300 (???? ??? ???????)');

return parseInt((b - mydate) / 1000);")

i get always '0' but if I replace the return to alert It works well. I tried to get it back to number and text var.