Nepali calendar also referred to as Nepali Patro is the official Bikram Sambat of Nepal. It uses lunar months and a solar sidereal year based on ancient Hindu tradition. The Bikram Samvat calendar is 56.7 years ahead (in count) of the solar Gregorian calendar.
In 1901 AD, the Rana monarchy of Nepal established the Bikram Sambat the official Hindu calendar, which began in 1958 BS. In Nepal, the new year begins on the first day of the month of Baishakh, which normally occurs between 13–15 April in the Gregorian calendar, and concludes on the final day of the month Chaitra.
In Nepal, the first day of the new year is a public holiday. Bisket Jatra, Bhaktapur’s annual carnival, is also held on Baishakh 1. Nepal Sambat, like Bikram Sambat, was designated as a national calendar in 2007.
The months have a minimum of 28 (typically Mangshir/Poush) and a maximum of 32 (usually Asar/Shrawan) days. In Nepali calendar, 12 months do not correspond to a sidereal year, corrective months (adhika masa) are added or (on rare occasions) deleted (kshaya masa).
A lunar year is divided into 12 months, with each month having two fortnights of varying lengths ranging from 29 to 32 days. The lunar days are referred to as tithis. Each month has 30 tithis that range in length from 20 to 27 hours.
The waxing phase, which begins on the day after the new moon (amavasya), is known as gaura or shukla paksha (the bright or auspicious fortnight). The fading phase is referred to as krishna or vadhya paksha (the dark fortnight, considered inauspicious).