The Isaric Calendar is the luni-solar system of dating and time-keeping used by Isars. It blends elements of the Persian Jalaali solar calendar with the Biblical lunar calendar. Significant features of the calendar are as follows: a lunar year that is dependent upon the solar year, which commences at the vernal equinox; 12 solar months with Latin-based names; civil events are timed according to the solar year, while religious events are timed according to the lunar year, which begins with the first New Moon (i.e., the first slither of a crescent) near the vernal equinox.
An Introduction to the Celestial Courses & the Divisions of Time
The first booklet to detail the Isaric calendar was, An Introduction to the Celestial Courses & the Divisions of Time, drafted in 2007 by bar-Karoza.