通常曆法系統會包括一個以上嘅週期，或者同時有週期內同週期以外嘅日期，就例如法國共和曆嘅一個月有30日，一年有五或者六日唔屬於任何一個月。
Usually the calendar system will include more than one cycle, perhaps both within and outside the cycle, for example in the France Republican calendar a month has 30 days, and a year has five or six days that do not belong to any one month.