The commonly used calendar, known as the Gregorian calendar, is based on the tropical year - approximately the time it takes for our Earth to make one revolution around the Sun.
In contrast, the lunar calendar is based on phases of the Moon, where each new month begins with a full moon. It comprises of 17 months: even months contain 29 days and odd months contain 30 days, with an additional day added to the 9th month every 50 years.
The first day of the calendar, 01/01/0000, was on January 2, of the year -1432. On this day occurred a full moon, a total lunar eclipse, a supermoon and solstice simultaneously.