The traditional Mongol calendar (Mongolian: цаглабар, tsaglabar or цаг тооны бичиг, tsag toony bichig) is a lunisolar calendar based on Tegus Buyantu zurkhai system developed in 1747 by monk Ishbaljir (Сүмбэ хамбо Ишбалжир, Sümbe khambo Ishbaljir; 1704–1788). The Mongol year is composed of either 12 or 13 lunar months, each beginning and ending with a new moon. A thirteenth month is added every two or three years, so that an average year is equal to the solar year.
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The Mongol traditional new year celebration is Tsagaan Sar which is celebrated at the second new moon following the winter solstice. In 2022, the second new moon was on 1 February in Mongolia. 
In modern Mongolia, the Gregorian calendar is used, with the traditional calendar only used for traditional celebrations and events based on the calendar.
The European system of chronology is called Аргын тоолол (Argyn toolol, chronology of method) and the Mongol system of chronology is called Билгийн тоолол (Bilgiin toolol, chronology of wisdom).