The national Indian calendar

Following up on a very specific request from the editor of this blog, I remain in India, or, at least, I keep writing about it.

The national Indian calendar, introduced in 1957, is an amalgam of over 30 different calendars adopted in Indian territory for centuries, some of which are still used for religious reasons.

The Indian calendar is a solar calendar very similar to our own Gregorian calendar. It has 12 months; the first, Chaitra, has 30 days on normal years and 31 on leap years; the following five months have all 31 days each; the last six month are all 30 days long. The year begins on our March 22nd (or March 21st, on leap years). Years are numbered within the Saka Era; the zero year of the Saka Era corresponds to 78 AD.

Today, November 1st, 2014, is Kartika 10th, 1936.

Amongst the many calendars that helped form the national Indian calendar, we can cite Nepali, Tamil, Bengali and Malayalam. In their vast majority, these calendars are Lunar (with no relation to the seasonal cycle), and slowly migrated to a lunissolar system. Almost all of them can be traced back to the calculations of the Surya Siddhanta, one of the oldest Astronomy texts of India (around 300 BCE).

There are 12 lunar months, which begin in the New Moon. These month are divided in two halves, the Pasksas, waxing and waning. The name of each month is related to a zodiac constellation; more specifically, to the constellation entered by the sun in that particular month.

Eventually, the sun will not enter any constellation in a given month. This month is then called Adhika Masa, literally “extra month”. In that year, we will have 13 months, and not 12.This is typical for a lunissolar calendar, although the intercalation rule is quite unique.

Indian calendars are not for beginners! ■