Imperial Calendar

The Imperial Calendar is the secondary civil calendar in Yamatai for cultural purposes and certain functions. The Imperial Calendar is essentially identical to the Unified Calendar in terms of length, except that the year begins and ends on the Empress of Yamatai's birthday. The year the Empress is born in is also considered Year 1 of a new era. There are no months in the Imperial Calendar. The current Imperial Year is 18, based on Empress Kameko's birth 17 years ago.

The use of the Unified Calendar is far more widespread due to its regularity.