calendrical

kalendaarinen Of, pertaining to, or used by a calendar system.
2009, Fred S. Kleine, Gardners Art Through the Ages: A Global History'', Thomson Wadsworth (2009), ISBN 9780495093077, http://books.google.com/books?id=CgWQWkE_3ocC&pg=PT387 page 371:

Although other ancient Mesoamerican societies, even in the Preclassic period, also possessed calendars, only the Maya calendar can be translated directly into today's calendrical system.

This growing focus on calendrical matters in early modern Europe paralleled, and in some measure directly influenced, a renewed interest among Jews in their own calendar.

In Vietnam, the calendrical system of "heavenly stems and earthly branches" sounds quite mystical and foreign, but this lunar calendar can in fact be translated quite simply into a Western calendar year with a formula and a chart.