BS to AD (and Back): How the Nepali Bikram Sambat Calendar Works

Nepal’s official calendar is Bikram Sambat (BS), a solar calendar running about 56 years and 8 months ahead of the Gregorian (AD) calendar — so mid-2026 AD is 2083 BS — and because its month lengths are set astronomically rather than by a fixed rule, converting BS ⇄ AD needs a real calendar table, not a formula. Convert any date both ways in the Nepali date converter.

What Bikram Sambat is

Bikram Sambat (विक्रम संवत्) is the official calendar of Nepal and is used across daily life there — government paperwork, newspapers, festivals, birthdays and the national fiscal year. Traditionally attributed to King Vikramaditya, its era begins in 57 BCE, which is why its year number runs well ahead of the Gregorian one: 2081 BS corresponds to 2024 AD, a gap of about 56 years and 8 months.

Because the offset isn’t a whole number of years, the exact difference shifts across the Gregorian year. From roughly mid-April (Nepali new year) to the end of December, the BS year is 57 ahead of the AD year; from January to mid-April it’s 56 ahead. That partial-year offset is the first thing that makes casual “just add 57” conversions unreliable.

Why the months don’t have fixed lengths

Here’s the part that surprises people used to the Gregorian calendar. Bikram Sambat is a solar calendar, but its months are defined by the sun’s passage through the signs of the zodiac rather than by a fixed count of days. A month lasts exactly as long as the sun spends in one sign — which varies between 29 and 32 days. So the length of, say, Jestha isn’t the same every year, and there’s no “30 days hath September” rule to memorise.

Those lengths are worked out by astronomical calculation and published each year in official almanacs (patro). This is precisely why a Nepali date converter can’t be a few lines of arithmetic the way a Gregorian leap-year check can: it has to consult a table of real month lengths for each BS year. Good converters embed a validated table covering roughly BS 1975 to 2099 (about AD 1918 to 2043).

The Nepali months

The twelve months, from the new year:

#	Month	Rough Gregorian span
1	Baishakh	mid-Apr → mid-May
2	Jestha	mid-May → mid-Jun
3	Ashadh	mid-Jun → mid-Jul
4	Shrawan	mid-Jul → mid-Aug
5	Bhadra	mid-Aug → mid-Sep
6	Ashwin	mid-Sep → mid-Oct
7	Kartik	mid-Oct → mid-Nov
8	Mangsir	mid-Nov → mid-Dec
9	Poush	mid-Dec → mid-Jan
10	Magh	mid-Jan → mid-Feb
11	Falgun	mid-Feb → mid-Mar
12	Chaitra	mid-Mar → mid-Apr

Nepal’s fiscal year runs from 1 Shrawan to the end of Ashadh (roughly mid-July to mid-July), and the major festivals track the BS calendar — Dashain falls in Ashwin/Kartik and Tihar shortly after — which is why their Gregorian dates move each year.

Converting a date, both ways

• AD → BS: pick the Gregorian date and the converter returns the Bikram Sambat year, month and day, with the weekday. Handy for turning an English-calendar birthday or deadline into its Nepali date.
• BS → AD: enter the BS year, choose the month (Baishakh…Chaitra) and the day, and get the Gregorian equivalent — for filling in English-calendar forms, visa dates or international bookings.

A worked anchor to sanity-check any converter: 1 Baishakh 2081 BS = 13 April 2024 AD (a Saturday, Nepali New Year 2081). Everything runs in your browser from the embedded calendar table — nothing you enter is uploaded, and it works offline.

Common BS ⇄ AD mistakes

1. Adding a flat 57 years — the offset is 56 or 57 depending on whether the date is before or after the mid-April new year.
2. Assuming fixed month lengths — BS months run 29–32 days and change year to year; only a real table converts them correctly.
3. Converting dates outside ~1918–2043 AD — the validated almanac data doesn’t extend there, so results become unreliable.
4. Mixing up the fiscal and calendar year — Nepal’s fiscal year starts in Shrawan, not on 1 Baishakh.
5. Expecting festival dates to be fixed in AD — Dashain and Tihar track BS, so their Gregorian dates shift annually.

Quick summary

Bikram Sambat is Nepal’s official solar calendar, about 56 years 8 months ahead of AD (2024 AD ≈ 2081 BS), with a new year on 1 Baishakh around mid-April and months of variable 29–32-day length set by astronomy — which is exactly why conversion needs an official month-length table rather than arithmetic. Convert any date both directions in the Nepali date converter, computed locally in your browser.

Related tools: calendar converter (Hijri, Hebrew, Persian and more) · days between dates. Conversion uses validated open Bikram Sambat calendar data (source).