The Hindu calendar system is based upon the motion of the moon.  Each lunar year comprises twelve months.  The lunar year comprises 354 days, compared to 365 ¼ days of the Gregorian calendar, which is based on the solar system.

This gap increases to a month over a period of three years.  For this reason, the Hindu lunar calendar has an extra month every three years, named Adhik.

The month of Adhik is considered to be more auspicious, and is referred to as the month of Purushottam, Bhagwan.  Those observing extra penance, bhakti and benevolence during this month gain extra blessings from God and their sins are washed away.  During this month auspicious events such as weddings are avoided.

The Hindu calendar year is based on the Vikram era, after King Vikram of Ujjain.  The system is still widely used in Northern and Western India.  The calendar began in 57-56 BCE.

The twelve months of the year are lunar-based, where each month is divided into the bright half (waxing of the moon), known as the ‘shukla’ or ‘sud’, and the dark half (waning of the moon), known as the ‘krishna’ or ‘vad paksh’.  The 15^th day of the sud half (full moon), is known as Punam, while the last day of vad half (new moon), is known Amãs.

In Northern India, the months end on the day of the full moon, while in Gujarãt, the months end on Amãs, the darkest night.  The lunar calendar, is approximately 354 days long.  To keep it synchronised with the solar calendar, in which years are approximately 365 days long, adjustments are made to the lunar-based calendar every 2.5 years.  This is achieved by adding an additional month called an ‘adhik’ or ‘Purushottam’ month to the calendar.

In Gujarãt, the Kãrtiki Samvat is used, where the new year begins after Divãli on Kãrtik sud 1.  The Ashãdhi Samvat still prevails in some parts of Rãjasthãn and Gujarãt – in Kutch and Saurãshtra.  In this system, the new year begins on Ashãdh sud 1.  The Vachanãmrut is written using the Ashãdhi Samvat.

The Common Era year corresponding to the Samvat year is obtained by subtracting 57 years from the Vikram year if the date falls between Ãshãdh sud 1 and December 31^st; and 56 years if the date falls between January 1^st and Jyeshtha vad 15.

The Hindu months and the Gregorian calendar months are as follows:

Chronological List of Festivals