docs: function dayOfYearFromWeeks(year, week, weekday, firstDayOfWeekOfYear, firstDayOfWeek) {
          var d = new Date(Date.UTC(year, 0)).getUTCDay(),
              daysToAdd, dayOfYear;
  
          weekday = weekday != null ? weekday : firstDayOfWeek;
          daysToAdd = firstDayOfWeek - d + (d > firstDayOfWeekOfYear ? 7 : 0);
          dayOfYear = 7 * (week - 1) + (weekday - firstDayOfWeek) + daysToAdd + 1;
  
          return {
              year: dayOfYear > 0 ? year : year - 1,
              dayOfYear: dayOfYear > 0 ?  dayOfYear : daysInYear(year - 1) + dayOfYear
          };
      }