Indian national calendar

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The Indian national calendar (sometimes called Saka calendar) is the official civil calendar in use in India. It is used, alongside the Gregorian calendar, by the Gazette of India, news broadcasts by All India Radio, and calendars and communications issued by the Government of India. Beside such formal purposes, the calendar is not very widely used.

The term may also ambiguously refer to the Hindu calendar, and the Saka era is commonly used by different calendars as well.

1 Calendar structure
2 Adoption
3 Rashtriya Panchang
4 See also
5 External links

[edit] Calendar structure

	Month	Length	Start date (Gregorian)
1	Chaitra	30/31	March 22*
2	Vaisakha	31	April 21
3	Jyaistha	31	May 22
4	Asadha	31	June 22
5	Sravana	31	July 23
6	Bhadra	31	August 23
7	Asvina	30	September 23
8	Kartika	30	October 23
9	Margashirsh (Agrahayana)	30	November 22
10	Pausa	30	December 22
11	Magha	30	January 21
12	Phalguna	30	February 20

In leap years, Chaitra has 31 days and starts on March 21 instead. The months in the first half of the year all have 31 days, to take into account the slower movement of the sun across the ecliptic at this time.

The names of the months are derived from older, Hindu lunisolar calendars, so variations in spelling exist, and there is a possible source of confusion as to what calendar a date belongs to.

Years are counted in the Saka Era, which starts its year 0 in 78. To determine leap years, add 78 to the Saka year - if the result is a leap year in the Gregorian calendar, then the Saka year is a leap year as well.

[edit] Adoption

The calendar was introduced by the Calendar Reform Committee in 1957, as part of the Indian Ephemeris and Nautical Almanac, which also contained other astronomical data, as well as timings and formulae for preparing Hindu religious calendars, in an attempt to harmonise this practice. Despite this effort, local variations based on older sources such as the Surya Siddhanta may still exist.

Usage officially started at Chaitra 1, 1879 Saka Era, or March 22, 1957. However, government officials seem to largely ignore the New Year's Day of this calendar in favour of the religious calendar [1].

[edit] Rashtriya Panchang

The Reform Committee also formalised a religious calendar, referred to as the Rashtriya Panchang. This, like many regional calendars, defines a lunisolar calendar based on the authoritative version of the Surya Siddhanta from the 10th century.

The word panchang is derived from the Sanskrit panchangam (pancha, five; anga, limb), which refers to the five limbs of the calendar: the lunar day, the lunar month, the half-day, the angle of the sun and moon, and the solar day.

In the Rashtriya Panchang, months are determined based on the sun's position against the fixed stars at sunrise, computed by antipodal observations of the full moon. This sidereal computation avoids fixed leap year rules, but the number of days in any given month can vary by one or two days. Conversion of dates to the Gregorian calendar, or computing the day of the week, requires one to consult the ephemeris. The lay person therefore relies on the panchangs or almanacs produced by authoritative astronomical schools.

Over time, different Brahminical bodies producing the panchangs have varied in their geographical center and other aspects of the computation, resulting in a divergence of a few days in the different regional calendars. Even within the same region, there may be more than one competing authority, occasionally resulting in disagreement on festival dates by as much as a month. The Rashtriya Panchang seeks to resolve such differences.