Amanta vs Purnimanta

Amanta and purnimanta — two ways to bound the same month

A lunar month is one cycle of the Moon, but a cycle has no natural “start” — you can begin counting at the new moon or at the full moon, and both are used. That single choice is the whole of amanta vs purnimanta:

• Amanta (“ending at the new moon”) — a month runs from one Amavasya to the next. Common in the south and west.
• Purnimanta (“ending at the full moon”) — a month runs from one Purnima to the next. Common in the north.

This page is the focused comparison of the two. For what a masa is, how it is named from the Sun’s sign, the six ritus and the Adhika leap month, read the masa page first — this one assumes it and drills into the single question the two reckonings disagree about.

Where they agree, and where they split

Split any lunar month into its two fortnights, exactly as under tithi:

• The Shukla Paksha (bright fortnight), new moon → full moon.
• The Krishna Paksha (dark fortnight), full moon → new moon.

Both systems put the bright fortnight in the same month — so through Shukla Paksha, amanta and purnimanta agree completely. The split appears only in the dark fortnight: purnimanta has already ended its month at the full moon and started the next one, so its dark fortnight belongs to the next month’s name. Amanta has not — its dark fortnight still belongs to the current month, because amanta only ends at the coming new moon.

The result: in the dark fortnight, the purnimanta month-name is exactly one month ahead of the amanta name.

The exact rule the engine uses

AstroShruti computes the amanta month first, then derives the purnimanta name from the paksha with a single rule:

• Shukla Paksha: purnimanta name = amanta name (they match).
• Krishna Paksha: purnimanta name = the month after the amanta name — the next entry in the twelve-month cycle, wrapping Phalguna → Chaitra.

That is the entire difference, and it is deterministic: the two names are either identical (bright half) or off by one step (dark half). The amanta name itself comes from the Sun’s sign during the month (the sankranti between the bounding new moons), as described on the masa page; the purnimanta name is then just this paksha-driven shift on top of it. If the month is an Adhika (leap) month, the Adhika prefix rides along on both names.

A worked example

The twelve months in order are Chaitra, Vaishakha, Jyeshtha, Ashadha, Shravana, Bhadrapada, Ashwin, Kartik, Margashirsha, Pausha, Magha, Phalguna.

Case 1 — a bright-fortnight (Shukla) day. Suppose the amanta month is Kartik. Since it is Shukla Paksha, the rule says the purnimanta name is the same: Kartik (amanta) = Kartik (purnimanta). No disagreement.

Case 2 — a dark-fortnight (Krishna) day. Suppose the amanta month is Ashwin. It is Krishna Paksha, so purnimanta is the next month: Ashwin (amanta) → Kartik (purnimanta). The very same calendar day — same tithi, same weekday, same Moon — is an Ashwin day to a southern almanac and a Kartik day to a northern one.

This is why a festival that falls in the dark fortnight can be quoted in two different months depending on the region, while the day itself never moves.

What is the same, and what is not

To keep it straight:

Only the last row differs. Amanta and purnimanta are a labelling convention on top of identical astronomy — never a different day, tithi or fortnight.

How AstroShruti shows both

For every date AstroShruti computes the amanta month from the lunar-month boundaries and then the purnimanta name from the paksha rule above, so the calendar carries both — for example a dark-fortnight day reading Shravana (amanta) · Bhadrapada (purnimanta). You read whichever your tradition uses, and you can see at a glance that they are one step apart only because it is the dark fortnight.

Open the Panchang for any date and place to see the amanta and purnimanta month side by side, with the paksha that decides whether they agree.

Common mistakes

• Thinking one name is “wrong.” In the dark fortnight both are correct; they are regional conventions, not an error to be reconciled.
• Assuming the tithi changed. It did not. Only the month-label shifts; the lunar day, paksha and nakshatra are identical.
• Expecting a difference in the bright fortnight. There is none — the two systems agree entirely through Shukla Paksha.
• Getting the direction backwards. In the dark fortnight it is purnimanta that runs ahead (one month later in name), not amanta.

Related concepts

• Masa — what a lunar month is, its solar naming, the ritus and the Adhika leap month. Read it alongside this focused comparison.
• Tithi — the lunar day and the two pakshas whose boundary decides whether the two names agree.
• Vara — the weekday; unchanged between the two reckonings, a useful check that only the month-label moved.