code: function passDays (date, term) {
    var from = this.from(date, term);
    return from ? this.diff(from, date, 'd') + 1 : null;
  }
docs: 指定した期間の経過日数を返します
  @method passDays
  @param  {DATE}   date
  @param  {String} term
  @return {Number} days