The calendar

Amanta and Purnimanta: why two panchangams disagree about the month

The single biggest cause of "your dates are wrong" in the Hindu calendar. Two conventions for where a lunar month begins, what the difference actually is, and how to tell which one your family follows.

Two people look at two panchangams. One says the day is Bhadrapada Krishna Ashtami. The other says Shravana Krishna Ashtami. Neither is wrong, neither has miscalculated, and both are describing exactly the same day, with exactly the same tithi, in exactly the same paksha. They simply disagree about which month it belongs to.

This is the amanta–purnimanta difference, and it is the cause of more confusion about Hindu dates than every other factor combined. It is also, once seen clearly, completely simple.

Where a month ends

A lunar month is the time the moon takes to go through one complete cycle of phases — roughly 29.5 days. Everyone agrees on that. What the two conventions disagree about is where in the cycle you put the boundary.

• Amanta — the month ends at amavasya, the new moon. 'Anta' means end; 'ama' refers to amavasya. So the month runs from the day after one new moon to the next new moon, and it begins with the waxing fortnight.
• Purnimanta — the month ends at purnima, the full moon. The month runs from the day after one full moon to the next full moon, and it begins with the waning fortnight.

Which fortnight is affected

Here is the part that matters in practice. For half of every month, the two conventions agree completely. For the other half, they differ by exactly one month name.

So a shukla paksha day is named identically by both. A krishna paksha day is placed by purnimanta in the following month, because for purnimanta that fortnight is the opening half of the next month rather than the closing half of the current one.

Who uses which

The split is broadly regional and has been stable for a very long time.

• Amanta: Andhra Pradesh, Telangana, Karnataka, Tamil Nadu, Kerala, Maharashtra, Goa, Gujarat and most of the south and west. The national civil calendar of India uses the amanta reckoning.
• Purnimanta: Uttar Pradesh, Bihar, Madhya Pradesh, Rajasthan, Haryana, Punjab, Uttarakhand, Chhattisgarh, Jharkhand and most of the north.

Nitya Deepam uses the amanta convention with Telugu masa names, because that is what our primary readership follows. Where a festival is commonly dated by the other convention, we note it on that festival's page rather than silently choosing.

A worked example: Krishna Janmashtami

Janmashtami falls on the krishna paksha ashtami — the eighth tithi of the waning fortnight — of the month containing it. That is a krishna paksha day, so it lands squarely in the zone of disagreement.

• In the amanta reckoning of the south, it is the Shravana krishna ashtami.
• In the purnimanta reckoning of the north, exactly the same day is the Bhadrapada krishna ashtami.

Both statements name the same date on the same Gregorian calendar. Nobody is celebrating on a different day. Only the month label differs. The same applies to Maha Shivaratri (Magha krishna chaturdashi in the amanta reckoning, Phalguna krishna chaturdashi in the purnimanta), to Holi, and to every other festival that falls in a waning fortnight.

How to tell which your family follows

Three quick tests, in order of reliability.

1. Ask which month Janmashtami falls in. Shravana means amanta; Bhadrapada means purnimanta.
2. Look at where your family is from. The regional split above is a good predictor and holds for the great majority of households.
3. Check the month name against a shraddha date. Ancestral rites are usually the observance families keep most conservatively, and the month name used for them is the family's real convention.

Adhika masa, the other complication

Twelve lunar months come to about 354 days, eleven short of a solar year. Left alone, the lunar calendar would drift through the seasons the way the Islamic calendar does. Hindu reckoning corrects this by inserting an extra month — adhika masa, also called mala masa or purushottama masa — roughly every thirty-two and a half months, whenever a lunar month passes without a solar sankranti falling in it.

The intercalary month takes the name of the month that follows it, prefixed with adhika, and the following month is then called nija ('true'). Festivals are observed in the nija month, not the adhika one. Ekadashi and other monthly vratams, however, occur in both — which is why an adhika masa year has twenty-six Ekadashis rather than twenty-four.

Both conventions insert adhika masa at the same point in the sequence, so it is not itself a source of disagreement between them — but it is one more reason a lunar date and a Gregorian date never map onto each other by a simple formula.

Every timing referenced in these guides is computed astronomically for the city you select and cross-referenced against the traditional panchangams in common use. How we compute