Bikram Sambat and the AD calendar
Bikram Sambat (BS) is Nepal's official calendar. Government letters, tenders, contracts, district rate books and the fiscal year are all dated in BS, while most software, drawings and international documents use the Gregorian (AD) calendar. BS runs about 56 years and 8 months ahead of AD. The BS year starts on 1 Baisakh, which falls on 13 or 14 April, so 14 April 2026 was 1 Baisakh 2083.
BS months follow the sun and are 29 to 32 days long. Their lengths change from year to year and are fixed by the Nepal Panchang Nirnayak Samiti, the national calendar committee, so there is no formula that converts a date by adding a fixed number of days.
How the conversion works
The converter holds a table of month lengths for every BS year it supports. It counts the days from 1 Baisakh of the right BS year to your AD date, then walks through the months of that year until the days run out. What is left is the day of the BS month.
Worked example: 28 September 2026. 1 Baisakh 2083 was 14 April 2026, 167 days earlier. Baisakh to Bhadra 2083 have 31, 31, 32, 31 and 31 days, 156 in all. The remaining 11 days run into Asoj, so the date is 12 Asoj 2083, a Monday, in fiscal year 2083/84.
Where it matters
Nepal's fiscal year starts on 1 Shrawan, in mid-July, so the date decides which year's budget, district rates and programme apply. Tender notices set submission deadlines in BS, contracts state completion dates in BS, and measurement books and site diaries are often kept in BS while scheduling software works in AD. Converting correctly keeps both records in step.
Common mistakes
Assuming every BS month has 30 days, or that 1 Baisakh is always 14 April: it moves between 13 and 14 April. The rule of thumb "add 56 years, 8 months and 17 days" is only approximate and is often a day or two off. Converting a timestamp in the wrong time zone: Nepal is UTC+05:45, so a time near midnight elsewhere can be a different date in Nepal. This tool works with calendar dates, and "today" means today in Nepal.
Month lengths for future years are provisional until the Samiti publishes that year's calendar. Published tables for years after 2086 BS already disagree by a day in some months, so check far-future dates against the official calendar.