ok....solved it by myself:
var date = new Date();var y = date.getYear();var d = date.getDate();var m = date.getMonth();var SJahr = y % 4;var SHJahr = y % 100;var S4Jahr = y% 400;var STag = ((S4Jahr == "0") ? (1) : ((SHJahr == "0") ? (0) : ((SJahr == "0") ? (1) : (0))));var days = new Array(31,28,31,30,31,30,31,31,30,31,30,31);if(STag == 1) days[1] += 1; var i, x;for(i = 0, x = 0; i < m; i++) { x += days[i];}//Result:var DayOfYear = x += d;