code: function setFurikaeKyujitu(year, holidays) {
    if (year < 1973) {
      return;
    }
    var last = null;
    var furikae = [];
    var activeTime = new Date(1973, 4-1, 29).getTime(); // 施行前日の祝日から適用
    var flg = false;
    var keys = Object.keys(holidays);
    keys.push('1231');
    keys.forEach(md => {
      var date = new Date(year, md.slice(0, -2) * 1 - 1, md.slice(-2) * 1);
      if (flg) {
        last.setTime(last.getTime() + A_DAY);
        if (last.getTime() !== date.getTime()) {
          furikae.push((last.getMonth() + 1) * 100 + last.getDate());
          flg = false;
        }
      } else {
        flg = date.getDay() === 0 && activeTime <= date.getTime();
      }
      last = date;
    });
    furikae.forEach(x => holidays[x] = '振替休日');
  }
docs: 振替休日を設定する
  施行: 1973/4/30-
  @method setFurikaeKyujitu
  @param  {Number}   year
  @param  {Object}   holidays