The Mists of Paoru
The calendar in use by all four nations was standardized by the Onmyoji at Chenmo in the year 1700 during the Second Cycle.
The standardized calendar features 12 months of 30 days each. There are 5 nationally recognized holidays in the empire and these are tacked onto the end of the months creating 5 months with 31 days. The years are named in the elemental cycle of Wood, Fire, Stone, Metal, and Water. The years run in pairs of the same element with the first symbolizing the Heavenly element and the following year the Material element.
There are 7 days of the week, each named for the 7 recognized spiritual elements in nature. The Week begins with Spirit Day, Wood Day, Fire Day, Stone Day, Metal Day, Water Day, and ends with Void Day. The belief is that the world began with spirit, which generated the elements who in turn generate and destroy each other before it descends into the Void. Void Day is seen as the day of contemplation and fasting where no work is done nor food or drink taken. The following day is Spirit Day which is generally held as a feast day wherein families join each other for great food, drink and music.