Nepal & Nepali jyotish

Vikram Sambat (BS) to AD conversion — how it actually works

Vikram Sambat runs roughly 56 to 57 years ahead of the Gregorian calendar, but the offset is not a constant you can add: Nepali months vary between 29 and 32 days and their lengths differ from year to year, so the day-to-day mapping shifts. A correct conversion needs the actual month lengths for the year in question, not arithmetic.

Sarathi Services TeamUpdated 8 September 2026

Written and reviewed by the team that builds the Jyotish Sarathi calculation engine.

Key takeaways

The year offset is about +56 (or +57 after the Nepali new year in Baisakh) — but that alone gives you the wrong date.
Nepali month lengths vary from 29 to 32 days, and vary between years, because the calendar is solar-sidereal rather than fixed.
So a BS date maps onto an AD date only via a table or a computation of that year's month lengths.
The Nepali new year falls in mid-April, around 13–15 April, not on 1 January.
For chart work the AD date is what matters, because an ephemeris is indexed by universal time.

What Vikram Sambat is

Vikram Sambat is the official calendar of Nepal. Its year begins in Baisakh, in mid-April by the Gregorian reckoning, and its twelve months are Baisakh, Jestha, Ashadh, Shrawan, Bhadra, Ashwin, Kartik, Mangsir, Poush, Magh, Falgun and Chaitra.

The important structural fact is that it is a solar-sidereal calendar: a month corresponds to the Sun's passage through one sidereal sign (a sankranti to the next). The Sun does not take the same number of days to cross each sign — the Earth's orbit is elliptical, so the Sun appears to move faster in some parts of the year and slower in others. Month lengths therefore come out unequal, and not identical from year to year.

Why "+56" is not enough

The mental shortcut most people use works only for the year, and only for part of the year:

Between 1 January and mid-April, the BS year is the AD year +56.
From mid-April (the BS new year) to 31 December, it is the AD year +57.
The day and month, however, do not map by any fixed offset at all.

The reason is the unequal month lengths. If a Gregorian month is always 30 or 31 days but a Nepali month can be 29, 30, 31 or 32, then the day-of-month correspondence drifts as the year progresses, and it drifts differently in different years. There is no formula of the form "BS date + n days = AD date" that holds across a year.

What you can shortcut	What you cannot
The year: +56 or +57 depending on whether the BS new year has passed	The day and month, which need that year's actual month lengths
Roughly which Gregorian month a Nepali month falls in	The exact date, which is what a birth chart depends on

Why this matters for a kundali

An ephemeris is indexed by universal time, so a chart is ultimately computed from an AD date and a clock time converted to UT. If a birth date recorded in BS is converted by hand and lands one day out, everything downstream moves: the Moon shifts about 13°, which changes its nakshatra, which changes the Vimshottari dasha balance and often the pada of several planets.

Doing it reliably

1Enter the date in the calendar it was recorded in. If the birth certificate says BS, type BS.
2Check the converted AD date against something independent if the case is important — a known festival, a weekday you remember.
3Watch the year boundary. A date in Chaitra (the last BS month) is in the earlier part of the Gregorian year, not the later one; getting this wrong is the most common off-by-one-year mistake.
4Record both. A cheena that prints the BS and AD dates together can be checked by anyone later.

In Jyotish Sarathi

BS dates can be entered directly wherever a date is asked for, and BS and AD are shown together in the patro and in the printed cheena. Conversion runs on the device with no internet connection — see the date converter.

Frequently asked questions

How many years is BS ahead of AD?

About 56 years before the Nepali new year in mid-April, and about 57 years after it. The year offset is that simple; the day and month are not, because Nepali month lengths vary from 29 to 32 days.

Why do Nepali months have different lengths?

Because Vikram Sambat is solar-sidereal: a month is the Sun's transit through one sidereal sign, and the Sun takes an unequal number of days to cross each sign. Month lengths therefore range from 29 to 32 days and are not the same every year.

When does the Nepali new year fall?

In mid-April, generally around 13 to 15 April in the Gregorian calendar, at the start of the month of Baisakh.

Can I enter a BS birth date to generate a kundali?

Yes. Jyotish Sarathi accepts BS dates directly and converts them internally to the AD date the ephemeris calculation needs, offline.