Solar, Lunar and Lunisolar

The entries record each system's structure (how many months, how long, how the year is kept in step with the Sun or allowed to drift), and where and by whom it is used. Seen together they lay out the small number of workable answers to a single astronomical problem and the very different religious lives built on each.

The astronomy the calendars rest on connects this section to Astrology & the Heavens and Vedic Astrology; the day-counts of Mesoamerica connect it to the divinatory day-signs treated under Divination Systems.