code: function getWeekYear(d, localeCode, iso) {
    var year, month, firstDayOfWeek, firstDayOfWeekYear, week, loc;
    year = getYear(d);
    month = getMonth(d);
    if (month === 0 || month === 11) {
      if (!iso) {
        loc = localeManager.get(localeCode);
        firstDayOfWeek = loc.getFirstDayOfWeek(localeCode);
        firstDayOfWeekYear = loc.getFirstDayOfWeekYear(localeCode);
      }
      week = getWeekNumber(d, false, firstDayOfWeek, firstDayOfWeekYear);
      if (month === 0 && week === 0) {
        year -= 1;
      } else if (month === 11 && week === 1) {
        year += 1;
      }
    }
    return year;
  }
docs: Week year helpers