The Hindu Calendar: Lunar Months, Samvat Years, Ritus and How Festival Dates Are Fixed

The Hindu calendar is called lunisolar because it listens to two clocks at once. The months follow the Moon, each running from one new moon to the next. The year follows the Sun, because the festivals are tied to the seasons and the seasons are tied to the Sun. Making the two agree is the main work of any panchang, the almanac that families and priests consult. This section explains how the pieces fit, and then gives one page for each of the twelve months.

The lunisolar year in plain words

A lunar month, the time from one new moon to the next, is about 29.5 days long. Twelve of them make about 354 days, which is roughly eleven days short of the solar year. Left alone, the festivals would drift through the seasons, and Holi would one day fall in the rains. To prevent that, the calendar adds a thirteenth month about once in every three years. It is called the Adhika masa, the extra month, and it repeats the name of an ordinary month.

The computed instants in this section show the effect. The lunar month of Chaitra begins at the new moon on 19 March 2026, 06:53 AM, and in 2027 it begins on 07 April 2027, 05:21 AM. That is 19 days later in the civil calendar, because 2026 carried the extra Adhika Jyeshtha. Every date on these pages is a computed new moon in Indian Standard Time, and the same new moon falls on the same civil date or a day either side depending on where in the world you stand.

Each month is divided into two halves. The bright half, Shukla paksha, runs from the new moon to the full moon, and the dark half, Krishna paksha, from the full moon to the next new moon. Each half has fifteen tithis, the lunar days that are the real units of the calendar; the pages in the tithi section describe them one by one.

The twelve lunar months

Each month is named after the nakshatra, or lunar mansion, in which the full moon usually stands. The names are old, and the match with the sky is approximate today, but the logic is simple: the full moon of Chaitra stands near the nakshatra Chitra, that of Kartika near Krittika, and so on around the year.

Each month page gives the festivals of that month, with links to the dates in the festivals section, and the start and end of the month in 2026 and 2027 in both the amanta and purnimanta ways of counting.

Amanta and purnimanta

Two systems exist for deciding where a month ends. In the amanta system, used in Maharashtra, Karnataka, Andhra Pradesh, Telangana, Goa and Gujarat, a month ends at the new moon. In the purnimanta system, used across most of the north, including Uttar Pradesh, Madhya Pradesh, Rajasthan, Bihar, Punjab, Haryana and Delhi, a month ends at the full moon. The bright half has the same name in both systems. The dark half gets a different name: what the south calls Ashwina Krishna paksha, the north calls Kartika Krishna paksha. That is why Diwali is in Ashwina on one calendar and in Kartika on another, though it is one night. The full explanation, with a table of well-known festivals in both labels, is on the amanta and purnimanta page.

Vikram Samvat and Shaka Samvat

Years are counted in eras, and two eras are in common use. Vikram Samvat is about 57 years ahead of the common era, and it is the era of most panchangs in the north and west. Shaka Samvat is about 78 years behind it, and it is the era of the national calendar used for official notices in India and of the Hindu calendar of Bali. In both, the year changes at Chaitra Shukla Pratipada, the first day of the bright half of Chaitra, in most of India, but in Gujarat the Vikram year changes in Kartika, the morning after Diwali.

The six ritus

The Indian year has six seasons, called ritus, each two lunar months long.

The ritus are the reason the extra month exists. A calendar that let the months slide would eventually put Vasanta in the monsoon. Ayurveda also divides the year by ritu, and the idea is the same in both: the season is the frame in which food, rest and observances are chosen.

Solar months in the south and east

Not every Indian calendar is lunar. In Tamil Nadu, Kerala, Bengal, Odisha, Assam and Punjab the main civil and religious calendars count solar months, each beginning when the Sun enters a sign of the sidereal zodiac. The Tamil months, beginning with Chithirai, the Malayalam months, beginning with Medam, the Bengali months, beginning with Boishakh, and the Punjabi months, beginning with Vaisakh, all start near the middle of April when the Sun enters Mesha. That is why several regional new years, Puthandu, Vishu, Pohela Boishakh and Vaisakhi, fall within a day or two of each other. Even so, temple festivals in those regions often follow the Moon, so the two systems run side by side. Each month page lists the solar months that overlap the lunar month.

How a festival date is fixed

A festival date is not a month and a number. It is a tithi and a moment of the day. The tithi is a lunar day, a thirtieth of the Moon’s cycle against the Sun, and it does not begin or end at sunrise: it can start at any hour and last from about 19 to 26 hours. Each festival names the part of the day in which its tithi must be in force. Ekadashi and many others ask for the tithi at sunrise. Ram Navami and Ganesh Chaturthi ask for midday. Diwali asks for the evening after sunset, Maha Shivaratri for the middle of the night, and Karva Chauth for moonrise.

Because sunrise, midday and moonrise differ from city to city, the same festival can fall on different civil days in different places. Where the tithi covers the named moment on two days, rules decide which day wins, and different traditions, such as Smarta and Vaishnava, use different rules. The festivals section shows the date for 49 cities, the any-city tool works one out for yours, and the method page sets out the calculation. For today’s tithi, nakshatra and timings, open the panchang.

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