ABSTRACT
There are three types of calendars: solar, lunisolar (a lunar calendar with adjustments made to make up for the missing days between it and the solar year), and lunar, and three types of chronologies: absolute (dating from the assumed beginning of the world), fixed (tied to an important event usually of political or religious significance), and variable (usually either regnally based or cyclical). The solar year lasts 365.25636 days (although there have been minute variants during the past five millennia), while the lunar year is approximately 354 days. Lunisolar calendars usually add on a set number of days or a month at given intervals in order to stabilize the months in their given seasons (known as intercalation).
