Names of the Months in the Indian Calendars

Helmer Aslaksen and Akshay Regulagedda

Names of the months

The complexity of the Indian calendar system is not just in the plethora of calendars available, but also in the manner in which they link up with one another. A principal point of linkage of most Indian calendars is in their names of the months; as we shall see, the similar sets of month names are used in more than one calendar. In this section, we aim to formulate rules determining the naming of the months. Our motivation is not just taxonomic; month names, we shall see, are critical to understanding the Indian calendar system.

We propose that there are two types of month names:

1) Months named after nakshatras

The set of month names named after nakshatras is used by both solar and lunisolar calendars, adding to seeming complexity of the Indian calendar system. Indeed, as we shall see, this type should actually called months initially named after nakshatras; there has been an infusion of solar rules into an essentially lunar convention.

Let us then, first consider the original rule. Saha and Lahiri mention that pakshas or fortnights were differentiated based on the nakshatra where the Moon is full [16]. That is to say, if a particular full Moon occurs near, say, the lunar asterism, Visakha, the full Moon would be called as Vaisakha Purnimasi, and the month would be Vaisakha. The earliest lunisolar months, then, were purnimanta, that is, the name of the full Moon corresponded to the name of the month. Of course, the full Moon occurs at all nakshatras. Fifteen were taken into account for naming of the month, spaced more or less equally.

We thus have the following set of names along with their respective nakshatras [17]:

Nakshatra on purnima Month name
Chitra Chaitra
Visakha Vaisakha
Jyestha Jyaistha
(Purva & Uttara) Aashaadha Aashaadha
Sravana Sraavana
(Uttara & Purva) Bhaadrapada Bhaadrapada
Asvini Asvayuja (Aasvina)
Krittika Kaarthika
Mrugasira Maarghasira
Pushyami Pausa (Pushyam)
Maghaa Maagha
(Uttara and Purva) Phalguni Phalguna

It may be noted that the months of Aashaadha, Bhadrapada and Phalguna are linked to two nakshatras respectively. Chatterjee and Chakravarthy give the following criteria for choosing nakshatras for month names [18]:

It must be mentioned that this rule now no longer matches the sky due to Earth's precession; for instance, this year's Chitra Purnimaasi had Swati as its nakshatra. Also, possibly for historical reasons, and allowing for regional variation in pronunciation, the Oriya, Bengali, Assamese, Punjabi and Tamil solar calendars also use the same set of month names. To reconcile all this, we might frame a new rule. The amanta lunar month takes its number from the solar month that starts in it, but its name from the solar month in which it starts, while following the purnimanta months in chronological order. That is to say, since Chitra occurred during the purnima of this year's first purnimanta month, we call this month as ‘Chaitra'. Consequently, the first amanta month would also be ‘Chaitra', which also would be the name of the solar month during which the amanta Chaitra started. However, the number of the solar month (1 in the case of amanta and purnimanta Chaitra) is not quite the same; the solar Chaitra is the last (i.e., 12th) month of the year. The lunisolar Chaitra's number is taken by the solar month that begins in it, namely the solar Vaisakha. All this can be seen in the picture below.

The relationships for all the months may be mapped according to the following table [19]. The Assamese, Punjabi and Tamil versions have been provided to give an idea of the linguistic variation.

Rasi Approximate
nakshatra on purnima
Lunar month name Solar month name Assamese version Tamil version Punjabi version [20]
Mesha Chitra Chaitra Vaisakha Bahag Chittarai Vaisakh
Vrshava Visakha Vaisakha Jyaistha Jeth Vaikasi Jeth
Mithuna Jyestha Jaishta Aashaadha Ahar Aani Harh
Karkata (Purva & Uttara) Aashaadha Aashaadha Sraavana Saon Aadi Sawan
Simha Sravana Sraavana Bhaadrapada Bhad Aavani Bhadon
Kanya (Purva & Uttara) Bhaadrapada Bhaadrapada Asvayuja (Aasvina) Ahin Purattaasi Asu
Tula Asvini Asvayuja (Aasvina) Kaarthika Kati Arppisi Katik
Vrischika Krittika Kaarthika Maarghasira Aghon Karthigai Maghar
Dhanus Mrugasira Maarghasira Pausa (Pushyam) Puha Maargali Poh
Makara Pushyami Pausa (Pushyam) Maagha Magh Thaai Magh
Kumbha Maagha Maagha Phalguna Phagun Maasi Phagun
Mina (Uttara and Purva) Phalguni Phalguna Chaitra Chait Panguni Chet

2) Months named after rasis

Only solar months share their names with rasis. Chatterjee and Chakravarthy give the following names along with the associated rasis [21].

Raasi Sanskritised Version Malayalam Version
Mesha Mesha Medam
Vrshava Vrshava Edavam
Mithuna Mithuna Midhunam
Karkata Karkata Karitaka
Simha Simha Chingam
Kanya Kanya Kanni
Tula Tula Thulam
Vrischika Vrischika Vrischikam
Dhanus Dhanus Dhanu
Makara Makara Makaram
Kumbha Kumbha Kumbham
Mina Mina Minam

That is to say, the month shares its name with that of its corresponding samkranti. For instance, if Mesha samkranti occurs on a certain day, then the period until the next samkranti would be Mesha masa (Medham masa).

This naming rule is followed primarily in the Malayalam calendar. Abhayankar says that the Oriya calendar also follows this rule [22].

Festivals

We provide a list of Indian festivals, along with their (Indian) dates and the calendar used to reckon the particular festival. The list of festivals is by no means exhaustive; the entries are mostly public holidays in India.

Festival [23] Indian date Additional rules Calendar
Makara samkranti, Pongal Makara samkranti None Solar
Maha Siva Raatri Magha K 14 Must cover a nisita Lunisolar
Holi Phalguna Purnima Holika Dahana is observed on the night of the Purnima; Holi is observed on the solar day after Holika Dahana Lunisolar
Ugadi, Gudi Padwa Chaitra S 1 None Lunisolar
Rama Navami Chaitra S 9 Must cover Madyahna  
Tamil New Year, Vishu, Bengali New Year Mesha samkranti Respective samkranti rules Solar
Ganesh Chaturti Bhadrapada S 4 Must cover Madyahna Lunisolar
Buddha Purnima Vaisakhi Purnima   Lunisolar
Raksha Bandan Sravana Purnima   Lunisolar
Janmashtami Sravana K 8   Lunisolar
Onam Moon is in Sravana nakshatra in Solar Bhadrapada   Lunisolar and Solar
Mahanavami Asvayuja S 9 Mahanavami is reckoned before the other 8 days of Dussehra [24] Lunisolar
Vijayadasami The tithi after Mahanavami Must cover a Nisita Lunisolar
Deepavali Asvayuja Amavasya Must cover pradosha Lunisolar

A bit of explanation is necessary. First, the terms. Nisita is defined to be a time-period measured by two ghatikas (1/60th of a solar day; approximately 20 minutes) stretching on either side of midnight. Pradosha is the time-period stretching for two muhurtas (1/15th of the time between sunrise and sunset; approximately 1 hour 36 minutes) after sunset. Madhyahna is one-third of the time-period between sunrise and sunset. This fraction covers mid-day.

Second, these dates are valid only on non-intercalary tithis for all lunisolar festivals. Both leap days and non-leap days in leap months are deemed unfit for festivals. (Kshaya masas are not an issue here because jugma months are deemed fit for religious observance and in the eastern and northwestern schools, the extra intercalary month is deemed to be normal.)

And finally, if the given tithi doesn't cover the given time, or covers the given time on two solar days, then the second solar day is reckoned to be the festival.

Bibliography

  1. K.D. ABHAYANKAR, Our Debts to our Ancestors, in "Treasures of Ancient Indian Astronomy" (ed. K.D. Abhayankar and B.G. Sidharth), Ajanta Publications, Delhi. 1993.
  2. Helmer ASLAKSEN, The Mathematics of the Chinese Calendar, preprint, National University of Singapore, 1999.
  3. Apurba Kumar CHAKRAVARTY and S.K. CHATTERJEE, Indian Calendar from Post-Vedic Period to AD 1900, in "History of Astronomy in India" (ed. S.N. Sen and K.S. Shukla), Indian National Science Academy, New Delhi, 1985.
  4. S.K. CCHATTERJEE, Indian Calendric System, Publications Division, Ministry of Information and Broadcasting, Government of India, 1988.
  5. Nachum DERSHOWITZ and Edward M. REINGOLD, Calendrical Calculations, Cambridge University Press, 2001.
  6. Nachum DERSHOWITZ and Edward M. REINGOLD, Indian Calendrical Calculations.
  7. Akshay REGULAGEDDA, Panchanga-Tantra: The Magic of the Indian Calendar System, Undergraduate Research Opportunities Programme in Science (UROPS) thesis, National University of Singapore, 2002.
  8. M.H. SAHA and N.C. LAHIRI, History of the Calendar in Different Countries Through the Ages (Part C of the Report of the Calendar Reform Committee), Council of Scientific and Industrial Research, New Delhi, 1992.
  9. Robert SEWELL and Sankara Balakrishna DIKSHIT, The Indian Calendar, Motilal Banarsidass Publishers Pte. Ltd., 1995.

Endnotes

Back to Helmer Aslaksen's page on Indian Calendars.


Helmer Aslaksen
Department of Mathematics
National University of Singapore
helmer.aslaksen@gmail.com

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