Amrutkaal Amanta vs Purnimanta: Two Ways to Reckon the Lunar Month
The Hindu lunar month can be counted two different ways, and which one a region uses changes the name of the month — though not the day itself. In the Amanta (अमान्त) system the month ends at the new moon (Amavasya) and a new month begins the next day; this is followed across South and West India. In the Purnimanta (पूर्णिमान्त) system the month ends at the full moon (Purnima), so a new month begins the day after the full moon; this prevails across most of North India. Both systems track exactly the same moon — the same tithis (तिथि) occur on the same days everywhere — but because they cut the cycle at different points, the bright and dark fortnights are paired into months differently. The practical consequence is that a single calendar day can sit in a month called, say, Shravana under one system and Ashadha under the other. This sounds confusing, yet it almost never affects when a festival is celebrated, because festivals are anchored to a tithi within a named fortnight, and the tithi falls on the same solar day regardless of which month-reckoning you use.
Where the Month Boundary Falls
A lunar month contains two fortnights: the waxing Shukla Paksha, ending at the full moon, and the waning Krishna Paksha, ending at the new moon. The two systems differ only in the order they pair these fortnights into a named month.
In Amanta reckoning, a month runs from the day after one new moon to the next new moon — so it begins with Shukla Paksha and ends with Krishna Paksha. In Purnimanta reckoning, a month runs from the day after one full moon to the next full moon — beginning with Krishna Paksha and ending with Shukla Paksha. The result is an offset: the dark fortnight (Krishna Paksha) that closes an Amanta month belongs to the start of the corresponding Purnimanta month, effectively carrying the next month's name.
Because of this, during the waning fortnight the two systems disagree on the month name by roughly one month, while during the waxing fortnight they generally agree. This is exactly why a North Indian and a South Indian panchang can print different month labels for the same date — most visibly in the dark half of the lunation.
Why Festivals Stay on the Same Day
A festival is defined by a tithi within a specific paksha — for example, the new-moon day of a particular month, or the eighth tithi of a dark fortnight. The tithi itself is determined by the angular separation of the Moon and Sun and falls on the same calendar day across all of India. The two month systems relabel the wrapper, not the contents.
So even when the month name differs, the festival lands on the same solar date. The classic example is Krishna Janmashtami, the eighth tithi of the dark fortnight: Purnimanta calendars place it in Bhadrapada while Amanta calendars place it in Shravana, yet both observe it on the very same day. The takeaway is that month names are a regional labelling convention; the underlying lunar reality — and therefore the observance — is shared.
Frequently Asked Questions
Which Indian regions use Amanta and which use Purnimanta?
Amanta, where the month ends at the new moon, is followed across South and West India. Purnimanta, where the month ends at the full moon, is followed across most of North India. The tithis themselves are identical in both.
If the systems differ, do festivals fall on different days?
No. Festivals are fixed to a tithi within a fortnight, and tithis occur on the same day everywhere. Only the month name may differ — the actual date of celebration is the same.
Why does Janmashtami appear in different months on different calendars?
It falls in the dark fortnight, the part of the cycle where the two systems disagree on the month name. Purnimanta labels it Bhadrapada and Amanta labels it Shravana, but it is the same day.