Sentence:  The year was divided up into twelve months renamed after the seasons [...]; each month comprised three ‘<WSD>decades</WSD>' of ten days – with the "décadi" replacing Sundays as a day of rest; and each day was reconsecrated to a natural product or farming tool or technique. 
Meaning of the word marked with <WSD> tags:  A period of ten days,  particularly those in the ancient Egyptian, Coptic, and French Revolutionary calendars. (from 18th c.)