The Hindu Calendar

Most of the world now lives by the Gregorian calendar, which follows only the Sun. The traditional Hindu calendar follows both. Its months are lunar, so each runs from one new moon to the next (or full moon to full moon) and lasts about 29.5 days. Twelve such months make about 354 days, roughly eleven days short of the solar year. If nothing were done, festivals would slowly drift through the seasons, as they do in a purely lunar calendar. The Hindu calendar corrects this by occasionally adding a thirteenth month.

Alongside the lunar months, panchangs also track solar months, which begin when the Sun enters a new zodiac sign (a sankranti). Makar Sankranti, when the Sun enters Capricorn, and Vaisakhi or Puthandu in mid-April, when it enters Aries, are solar festivals; that is why they fall on nearly the same Gregorian date every year, while Diwali and Holi move about.

There is no single Hindu calendar. Regional calendars differ in when the year begins, how months are counted and which era is used, but they share the same astronomical framework of tithis, nakshatras and months.

The lunar months take their names from the nakshatra near which the Moon is full in that month: the full moon of Chaitra falls near Chitra, of Kartika near Krittika, and so on. Over many centuries the match has drifted a little, but the names remain. The Gregorian ranges below are approximate because the lunar months shift by up to a few weeks from year to year.

Indian calendars disagree on one small but important point: whether a month ends on the new moon or the full moon.

In the Amanta system (ending on amavasya), used in most of the peninsular and coastal states such as Maharashtra, Gujarat, Karnataka and Andhra Pradesh, a month runs from the day after one new moon to the next new moon. Its bright half comes first, then its dark half.

In the Purnimanta system (ending on purnima), used in Nepal and most of India north of the Vindhyas, a month runs from the day after one full moon to the next full moon, so the dark half comes first.

The bright half (Shukla paksha) carries the same month name in both systems. Only the dark half (Krishna paksha) is named differently, falling in the next month in the Purnimanta system. Maha Shivaratri is the classic example: the same night is Magha Krishna Chaturdashi in an Amanta panchang and Phalguna Krishna Chaturdashi in a Purnimanta one. Likewise, Janmashtami is Bhadrapada Krishna Ashtami in the north and Shravana Krishna Ashtami in Amanta reckoning. The festival is the same; only the label changes. When reading a vrat katha or a panchang, it helps to check which system it uses.

Because twelve lunar months fall about eleven days short of a solar year, the gap builds up. Roughly every 32.5 months, a little under three years, a lunar month passes in which the Sun does not enter a new zodiac sign at all. That month has no sankranti, and it is declared Adhik Maas (the 'extra' month). It takes the name of the month that follows it, so an Adhik Ashvin is followed by the regular (nija) Ashvin. The extra month pulls the lunar calendar back into line with the seasons.

Adhik Maas is also called Mala Maas, and in devotional tradition Purushottam Maas, the month dedicated to Vishnu. Families usually avoid starting weddings, griha pravesh and similar ceremonies in it, while devotees use it for extra japa, reading scripture, charity and fasting.

Very rarely the opposite happens: a lunar month contains two sankrantis and a month is dropped (kshaya maas). This is uncommon, with gaps usually of a century or more.

Hindu calendars count years in eras (samvat). The two most widely used are Vikram Samvat and Shaka Samvat.

Vikram Samvat begins in 57 BCE, so its year number is usually 57 years ahead of the Common Era (56 years ahead for the part of the year before the new year). Tradition credits King Vikramaditya of Ujjain with founding it after a victory over the Shakas. Historians note that the name 'Vikrama Samvat' does not appear in inscriptions before about the 9th century, and the same era was earlier known as Krita or Malava. It is widely used in North and West India and is an official calendar of Nepal. Its new year is kept on Chaitra Shukla Pratipada in North India, while in Gujarat the new year falls on Kartika Shukla Pratipada, the day after Diwali.

Shaka Samvat begins in 78 CE, so subtracting 78 from the Common Era year gives the Shaka year (79 in the months before the Shaka new year). It is common in old South Indian inscriptions and in many panchangs. In 1957 the Government of India adopted a reformed Shaka calendar as the Indian national calendar, on the recommendation of the Calendar Reform Committee chaired by the scientist Meghnad Saha. It began on 1 Chaitra 1879 Shaka, which was 22 March 1957. In the national calendar, 1 Chaitra falls on 22 March, or 21 March in a leap year. It is used in the Gazette of India and government communications alongside the Gregorian date.

Indian tradition divides the year into six seasons (ritus) of two months each, rather than the four seasons familiar in Europe. Sanskrit poetry celebrates them; Kalidasa's Ritusamhara is a whole poem on the six seasons. Festivals follow them too: Vasant Panchami greets spring, and Sharad Purnima marks the clear autumn moon. The lunar months below are the traditional pairing; dates are approximate.

A full traditional date strings these pieces together: era and year, month, fortnight, tithi and weekday. A sankalpa recited before a puja often names them in just this order, placing the worshipper precisely in time. A panchang heading might read, for example, 'Vikram Samvat …, Kartika, Krishna paksha, Amavasya, Somvar'. When you see such a date, first check whether the panchang is Amanta or Purnimanta, then match the tithi; the weekday and the Gregorian date printed beside it will confirm the rest.

Our page on the panchang explains the tithi, nakshatra, yoga and karana in detail.