Nepal
Sambat, Bikram Sambat and adjustment.

Calendar –
Sambat/Samvat/Samwat.

Tilak B.
Shrestha, Ph.D.                    tilakbs@hotmail.com             October 2009 

Nepal Sambat (NS) is basically
a lunar calendar adjusted to the solar cycle – lunisolar. Its association with
the Moon phase makes it an ideal calendar for the Dharmic festivals. Bikram
(Vikram) Sambat (BS) is a Solar calendar ideal for seasonal issues like
planting/harvesting, and official events.

Lunar NS and
Solar BS caters for different needs and do not compete. That is NS and BS do
not substitute each other. Thus, we must promote both calendars: NS for Dharmic
festivals and BS for official events. We also need to use the solar Gregorian
calendar to communicate in international level. Most of the business people in Nepal
close the old and begins new account according to NS. Thus, it could be the
ideal as the fiscal year.

NS is an
indigenous Nepalese creation with its own legend. It is a pride of all
Nepalese. It does not belong only to Newar community. NS usually begins on the
day after Laxmi Puja or Gobardhan puja day or ‘Mha’ Puja day of Newar
community.  It was initiated in the reign of King Raghav Deva on October 20, 879 AD. The first day of
1130 NS is on October 19, 2009.

The legend
associated with NS goes that a commoner Sankhadhar Sakhwa made lots of money by
converting sand from Bishnumati river to gold, paid every body’s debt, and made
all Nepalese free of debt then. To commemorate the occasion (national, economic
and spiritual) the Sambat was instituted. Historians or chemists may dispute a
few finer points. However, they are not important and best left to the
academicians. The importance of the legend is the very idea of a simple man
rising to the occasion and contributing in the national level. He remains our
ideal and a source of inspiration. He is recognized in the list of the heroes
of Nepal
"Nepali Bivuti” by the Government on November 18, 1999.

BS is
instituted by the ancient Emperor Vikramaditya to commemorate his victory over
the invading Sakas. The first day of 2066 BS is on April 14, 2009.

Earlier, NS
was the prominent among other Sambats used in Kathmandu
valley. Though it is ideal for Dharmic festivals, being a lunar calendar it’s
dates repeats and skips frequently. Besides, every 3 years an extra month
needed to be added. The other prominent calendar in use then was the solar Saka
Sambat. King Prithvi Narayan used Saka Sambat as the official calendar. Later,
Chandra SJB Rana replaced Saka Sambat with BS as the official calendar in 1903
AD. BS being older than both Saka and Gregorian gives the sense of antiquity
and perceived importance.

The Solar
year or the sun coming to same position as per distant stars, which defines the
seasons, is 365.2424 days. The Lunar month or the ‘synodic period’ between same
phases of Moon is 29.530589 days. Both these numbers differs from the actual
period ‘sidereal’ of revolution. But these numbers are relevant for the
calendars. Presently, the annual equinoxes are on March 20 (Spring) and
September 22 (Autumn). The solstices are on June 21 (Summer) and December 21
(Winter). Even in the ancient times, the 365 days in a year is recognized and
calendars are devised as such. However, recognition of the fraction 0.2424
rendered different ingenuous solutions.

Twelve lunar
months makes only 354.36 days. Thus, the lunisolar NS is adjusted to the solar
cycle by adding one extra month every 3 years. It gives 364.21 for a year. NS
is pegged to the observed Sun’s position against the stars and additional
adjustments are rendered by adding or loosing a lunar month once a while.

BS is also
pegged to the observed Sun’s position against the stars. Its months have
anywhere from 28 to 32 days. Aligning it to the solar year is done by adjusting
the number of days of the months. It does not use rule-based leap year. One of
the ancient Hindu treaties on the astronomy describing the computation is the
‘Surya Siddhanta.’

Currently the
solar Gregorian calendar is the internationally used system. It adjusts to the
solar cycle using rule-based leap year. It has 365 days in the common year and
366 days in the leap year. It uniquely improves on the earlier Julian calendar
by an imaginative leap year rule. In Julian calendar every 4rth year is the
leap year. Thus it accounts for 365.25 days. The unaccounted fraction 0.0076
days off sets it over a week in a millennium.

The Gregorian
calendar tries to fix it with the new rule: Every year that is exactly
divisible by four is a leap year, except for years that are exactly divisible
by 100; the centurial years that are exactly divisible by 400 are still leap
years. For example, the year 1900 is not a leap year; the year 2000 is a leap
year.

Thus, it
repeats completely every 146,097 days, which fill 400 years, and which also
happens to be 20,871 seven-day weeks. Of these 400 years, 303 (the "common
years") have 365 days, and 97 (the leap years) have 366 days. This gives
an average year length of exactly 365.2425 days. Thus it is longer by 0.0001
day. In one millennium it off sets only by 0.1 day. Or, it will off set by a
day after 10 millenniums.

Pope Gregory
XIII instituted the calendar in 1582. The Julian calendar was already off set
by almost 10 days then. Thus, the Gregorian calendar takes off about 10 days to
adjust it back. However, its acceptance was quite slow. British
Empire including America
adopted it only in 1752. It is interesting to note that the adoption was quite
confusing. The day after September 2,
1752 (Wednesday) became Sept
14, 1752 (Thursday).

The recent news on possible
adjustment of Bikram Sambat provokes a few suggestions. Perhaps we can have the
spring equinox as the first day of the year, fix the days in the months, and
use Gregorian style leap year rule. Currently BS New Year falls usually on
April 14. Move it to the spring equinox (March 20 in 2009). It can be done
painlessly by having only 31 days in the months with 32 days. After a few years
the New Year will slide back to the equinox. Fix the days of the month using 30
and 31 days in sequence, except for the last month. That is 30 days for
Baisakh, Ashad, Bhadra, Kartik, Poush and Falgun; and 31 days for Jestha,
Shrawan, Aswin, Mangshir and Magh. The last month Chaitra will have 30 days in
general and 31 days in the leap year. It will give 365 days for a year in
general and 366 days in the leap year. The leap year to follow the rule of the
Gregorian system. That is, the next leap year will be 2012 BS and the month of
Chaitra will have 31 days. It makes conversion between BS and Gregorian easy.
Also we should keep an eye on the position of the sun relative to the stars.
Bikram Sambat can be fine tuned by appropriate correction as per the location
of the sun on the leap year, above the standard rule.

Perhaps our Nepal
Academy ‘Pragna Pratisthan’ should
take initiative on it. FYI, here is the converter between BS and Gregorian
calendars: http://www.ashesh.com.np/nepalicalendar/

May Bhagwan
Surya Deva enlighten us all.