Indian Calendars Leow Choon Lian
Source: http://www.math.nus.edu.sg/aslaksen/projects/lcl.pdf
Helmer Aslaksen
Department of Mathematics
National University of Singapore
helmer.aslaksen@gmail.com
The Indian Calendars
I'm currently working on a paper on the Indian calendar, with an emphasis on computing the date of Deepavali and regional varieties. In the meantime you can look at these papers.
- When is Deepavali (Diwali)?
- Regional Varieties of the Indian Calendars
- Names of the Months in the Indian Calendars
- Skipped (kshaya) Months in the Indian Calendars
The Indian calendars are very interesting, but very complicated. Indians use both solar and lunisolar calendars. The solar calendars follow the sidereal year. The lunisolar calendars are of two types; some have months that run from new Moon to new Moon, while some have months that run from full Moon to full Moon. In addition to leap months, the lunisolar calendars sometimes skip months. They also follow the Moon for the days, so sometimes they skip or add days. They are probably the most complicated calendars currently used in the world. There are also several regional variations.
A basic reference is the book Calendrical Calculations by Nachum Dershowitz and Edward M. Reingold. Unfortunately, the first edition had some weaknesses in the chapters on the Indian calendar, but this has been corrected in the second edition. However, their main emphasis is to code the Surya Siddhanta algorithms, and they are not interested in regional varieties. For more details, you may want to try to get hold of the book Indian Calendric System by Commodore S.K. Chatterjee (Retd.).
One of my honours students, LEOW Choon Lian, has written a project on Indian Calendars. She has also written a Mathematica package,IndianCalendar.m. It uses the code of Nachum Dershowitz and Edward M. Reingold from their book Calendrical Calculations. Their Lisp functions were translated into the Mathematica package Calendrica by Robert C. McNally. Please note that this is the code from the first edition, which is freely available. The code from the new edition will only be available with the book.
The Mathematica notebook IndianCalendar.nb demonstrates the commands. (If you don't have Mathematica, you can download a copy of theMathReader.)
I have also supervised a number of undergraduate research projects on the Indian calendars.
- Daphne CHIA, Indian Calendars: Comparing the Surya Siddhanta and the Astronomical Ephemeris, 2001.
- Akshay REGULAGEDDA, Panchanga-Tantra: The Magic of the Indian Calendar System, 2002.
- Akhil DOEGAR and Akshay PRASAD, Indian Calendars, 2002.
If you know much about the different regional variations of the Indian calendar, I would love to hear from you.
Back to Helmer Aslaksen's page on Calendars in Singapore.
Helmer Aslaksen
Department of Mathematics
National University of Singapore
helmer.aslaksen@gmail.com
06/28/2012 03:38:09 http://www.math.nus.edu.sg/aslaksen/calendar/indian.html
India is a vast country consisting of altogether 35 states and union territories. With a long
civilization and hence a rich history, the country naturally developed its own methods of
time keeping. Due to cultural diversification, these methods vary in different regions and
variations in the Indian (Hindu) calendar-making emerged.
Today, there are several calendars being used in India. The government uses the
Gregorian calendar for administrative purposes. The Muslims use the Muslim (Islamic)
calendar. The Indian solar and lunisolar calendars, including their variations, are used for
both civil and religious purposes and hence exert great influence on the daily activities of
the people of India. The aim of this thesis is to describe the workings of the Indian solar
and lunisolar calendars. The rules and principles that guide the calendars will be
explained in a simple and systematic way for readers to understand.
The first chapter introduces basic astronomical concepts required to understand
the fundamental units of time, namely, the day, the month and the year. In the second
chapter, we start to classify calendars into solar, lunar and lunisolar calendars. In the last
chapter, we will focus on the conventions that are used for making the Indian solar and
lunisolar calendars. We start with a brief introduction of the Indian calendars which are
used in India. Then we proceed with the discussion of the Indian solar and lunisolar
calendars respectively. Finally, we present a number of computer codes to generate the
dates of some Indian solar and lunisolar calendars.
Read on...