code: function RecurrenceRule(year, month, date, dayOfWeek, hour, minute, second) {
    this.recurs = true;
  
    this.year = (year == null) ? null : year;
    this.month = (month == null) ? null : month;
    this.date = (date == null) ? null : date;
    this.dayOfWeek = (dayOfWeek == null) ? null : dayOfWeek;
    this.hour = (hour == null) ? null : hour;
    this.minute = (minute == null) ? null : minute;
    this.second = (second == null) ? 0 : second;
  }
docs: /* RecurrenceRule object /*
  Interpreting each property:
  null - any value is valid
  number - fixed value
  Range - value must fall in range
  array - value must validate against any item in list
  
  NOTE: Cron months are 1-based, but RecurrenceRule months are 0-based.