THE BLOG · EXPLAINER

why ur festival is named a different month in delhi

half the country ends the lunar month at the new moon and half at the full moon. the sky is identical, the dates are almost always identical, and the month names are not. here is the whole thing, and the one case where the day really does differ.

SEPTEMBER 23, 2026 · 10 MIN READ

ur family calls it kartik. ur cousins in pune call the same night ashwin. neither of u is wrong and neither of u has ever been told why.

there are two conventions for where a lunar month ends. that is the entire disagreement. it has been running for well over a thousand years and it explains almost every calendar argument in an indian family group chat.

here is the mechanism, the map of who uses which, and the one situation where the day itself genuinely differs.

the short version

an amanta month ends at the new moon. a purnimanta month ends at the full moon.
amanta is the norm across the south and west. purnimanta is the norm across the north.
the bright fortnight is named identically in both. only the dark fortnight gets a different month name.
so janmashtami is bhadrapada krishna ashtami in delhi and shravana krishna ashtami in mumbai. same night.
the actual date almost never differs. when it does, it is a tithi-at-sunrise rule, not this.
neither is a mistake. both are documented conventions for labelling the same sky.

quick facts

Amanta: Month ends at Amavasya, the new moon. From ama plus anta, new-moon ending.
Purnimanta: Month ends at Purnima, the full moon.
Amanta regions: Gujarat, Maharashtra, Karnataka, Andhra Pradesh, Telangana, Tamil Nadu, Kerala.
Purnimanta regions: Uttar Pradesh, Bihar, Madhya Pradesh, Rajasthan, Punjab, Haryana, Uttarakhand, Himachal.
What differs: The month name attached to the dark fortnight. Nothing else.
What never differs: The tithi, the moon's actual position, and any birth chart.
Lunar year length: About 354 days, roughly 11 short of a solar year.
The correction: Adhik maas, an extra month inserted roughly every 32 to 33 months.

two ways to end a month

A lunar month is one full cycle of the moon, about 29.5 days. But a cycle is a circle, and a circle has no natural starting point. Two conventions emerged: cut it at the new moon, or cut it at the full moon.

every lunar month contains two fortnights. shukla paksha is the bright half, from new moon to full moon, when the moon is growing. krishna paksha is the dark half, from full moon to new moon, when it is shrinking.

the two conventions simply put the scissors in different places.

	amanta	purnimanta
Month runs	new moon to new moon	full moon to full moon
Month opens with	shukla paksha, the bright half	krishna paksha, the dark half
Month closes with	krishna paksha	shukla paksha
Named after	ama + anta, new moon ending	purnima + anta, full moon ending

that is the whole difference. everything downstream falls out of it automatically.

why only the dark fortnight shifts

Because both conventions agree on where the bright fortnight sits, a given shukla paksha carries the same month name in both. But the dark fortnight that follows it belongs to the same month under amanta and to the next month under purnimanta, so its name shifts by one.

work through it once and it stops being confusing forever.

take the bright fortnight of ashwin. both systems call it ashwin shukla paksha. no argument.

now the moon goes full and starts shrinking. under amanta, the month has not ended yet, because it ends at the new moon. so this dark fortnight is still ashwin. it is ashwin krishna paksha.

under purnimanta, the month ended the moment the moon went full. so this same dark fortnight opens the next month. it is kartik krishna paksha.

same fortnight. same nights. same tithis. one is filed under ashwin and one under kartik, and both filings are correct within their own system.

the same festivals, under two names

Every festival that falls in a dark fortnight gets two month names. The date is identical, the tithi is identical, and only the label changes. Festivals in the bright fortnight are named the same in both systems.

festival	tithi	purnimanta name	amanta name
Krishna Janmashtami	Krishna Ashtami	Bhadrapada	Shravana
Maha Shivaratri	Krishna Chaturdashi	Phalguna	Magha
Dhanteras	Krishna Trayodashi	Kartik	Ashwin
Diwali	Krishna Amavasya	Kartik	Ashwin
Holi (Holika Dahan)	Shukla Purnima	Phalguna	Phalguna
Navratri (Sharad)	Shukla Pratipada onward	Ashwin	Ashwin

look at the bottom two rows. holi and navratri fall in the bright fortnight, so both systems agree completely. every disagreement in that table is in a dark fortnight, which is exactly what the mechanism predicts.

this is why dhanteras is a kartik festival in a delhi household and an ashwin festival in a pune one, on the same evening, in the same year.

who uses which

Broadly, the south and west of India use amanta and the north uses purnimanta. The boundary is not a neat line and communities that migrated carry their convention with them, which is why a single city can contain both.

convention	where it is the norm
Amanta	Gujarat, Maharashtra, Goa, Karnataka, Andhra Pradesh, Telangana, Tamil Nadu, Kerala
Purnimanta	Uttar Pradesh, Bihar, Jharkhand, Madhya Pradesh, Chhattisgarh, Rajasthan, Punjab, Haryana, Uttarakhand, Himachal Pradesh

and it is worth saying that this is a convention about naming, not about belief. two households observing the identical festival on the identical night, filing it under different month names, are not practising different religions. they are using different filing systems.

adhik maas, and the eleven day problem

Twelve lunar months come to about 354 days, roughly eleven short of a solar year. Left alone, festivals would drift through the seasons. Adhik maas, an extra lunar month inserted roughly every 32 to 33 months, is the correction.

this is the reason ur festivals move about eleven days earlier each year and then jump forward again.

the rule is elegant. a lunar month that contains no sankranti, no entry of the sun into a new sidereal sign, is declared an extra month. it gets the same name as the month following it, prefixed adhik, and the normal one is called nija, the true one.

during an adhik maas most auspicious activity is traditionally paused: no weddings, no house entries, no new ventures. that is a real, documented convention, and it is a good example of the tradition genuinely restricting a window, which makes the modern retrograde version look even less like scripture by comparison.

the very rare opposite, kshaya maas, drops a month entirely. it can only occur in a narrow part of the year and turns up about once a century. the festival dates explainer goes through the lunisolar arithmetic in full.

when the day genuinely differs

Amanta and purnimanta change the name, not the date. Real one-day differences come from a separate rule: which tithi governs a day when the tithi changes close to sunrise.

this is the part worth understanding, because it is the actual source of the argument about which day is correct.

a tithi runs about 19 to 26 hours, so it almost never lines up with a calendar day. every panchang needs a rule for which tithi owns a given day, and the rules differ:

the tithi current at sunrise governs the day. this is the most common rule.
for some observances, the tithi current at a specific time matters instead: pradosh kaal for dhanteras, midnight for janmashtami, moonrise for karva chauth.
where a tithi spans two sunrises or none, traditions apply different tie-breaks.

so when two calendars genuinely disagree about a date, it is nearly always this and not amanta versus purnimanta. and it is why fasting festivals with a time-of-day requirement are the ones that split most often.

and then there are the solar calendars

Several regional calendars are solar rather than lunar. They count months by the sun's entry into each sidereal sign, so their dates barely move against the gregorian calendar at all.

tamil, bengali, malayalam, odia, assamese and punjabi calendars all work this way, which is why their new year lands in mid april every year with almost no drift. puthandu, pohela boishakh, vishu, vaisakhi: same week, every year.

that stability is the giveaway. a festival that moves eleven days a year is lunar. one that sits on roughly the same april date forever is solar, tracking the sun's entry into mesha.

so india runs at least three calendar systems side by side, and a single family can easily be using all three: a solar new year, lunar festivals, and a gregorian work calendar. none of this is confusion. it is three instruments measuring three different things.

myths, one at a time

One of the two conventions is the correct one.

Both are documented and both are internally consistent. They label the same astronomy differently.

Amanta and purnimanta make festivals fall on different days.

They change the month name, not the date. Real date splits come from tithi-at-sunrise rules.

This affects my birth chart.

It cannot. A chart is computed from exact planetary longitudes. Calendar labels never enter the calculation.

Adhik maas is inauspicious.

It is a correction, inserted to stop the lunar year drifting through the seasons. Certain activities are traditionally paused in it, which is a convention rather than a warning.

Every Indian calendar is lunar.

Several major regional calendars are solar and barely drift at all, which is why their new year is always mid April.

Holi is in a different month depending on region.

Holi falls in the bright fortnight, so both conventions call it Phalguna. Only dark fortnight festivals get two names.

faq

what is the difference between amanta and purnimanta?

where the lunar month ends. an amanta month ends at the new moon, a purnimanta month ends at the full moon. same sky, two conventions, and they name the dark fortnight differently as a result.

which parts of india use which?

amanta is the norm across the south and west, including gujarat, maharashtra, karnataka, andhra, telangana, tamil nadu and kerala. purnimanta is the norm across the north, including up, bihar, madhya pradesh, rajasthan, punjab and haryana.

does this change the actual festival date?

almost never. the tithi is the same tithi and the day is the same day. what differs is which month name that day is filed under, so a purnimanta calendar calls it bhadrapada while an amanta one calls it shravana.

why is janmashtami in a different month depending on who i ask?

because it falls in the dark fortnight. krishna janmashtami is bhadrapada krishna ashtami in the north and shravana krishna ashtami in the west and south. one day, two names.

is the bright fortnight the same in both systems?

yes. shukla paksha carries the same month name in both conventions. only the dark fortnight, krishna paksha, gets shifted by one month name.

so which one is correct?

both. they are two regional conventions for labelling the same astronomy, and neither is a mistake. classical texts exist supporting each.

what is adhik maas?

an extra lunar month inserted roughly every 32 or 33 months, so the lunar year does not drift away from the seasons. a lunar year is about eleven days short of a solar one and adhik maas is the correction.

what is kshaya maas?

the rare opposite, where a lunar month is dropped entirely. it can happen only in a narrow part of the year and only every century or so.

can the actual day ever differ between two regions?

yes, occasionally. it happens when a tithi changes close to sunrise and the two panchangs apply different rules about which tithi governs the day. that is a genuine one-day difference rather than a naming one.

do solar calendars use this too?

no. tamil, bengali, malayalam and punjabi solar calendars count months by the sun's entry into each sidereal sign, which is why their new year lands in april and does not move much.

does this affect my kundli?

no. a birth chart is computed from exact planetary positions, not from calendar labels. amanta and purnimanta are naming conventions and they never touch the maths.

how do i know which convention my family uses?

check what ur family calls the month that diwali falls in. purnimanta calls it kartik, amanta calls it ashwin. same festival, same night.