Between the Bhishma system and the current system based on Sun’s transit through rashi, thousands of years have passed. Was any refinement of Bhishma’s system introduced, such as, taking one extra month after 29 normal months? If so, when and by whom? Not known. If there was any such change, there must be somewhere a record of who introduced the change and more particularly, when.
There is a common belief among all researchers that on purnima day of any lunar month, the moon is in the Nakshatra whose name the month carries, e. g. in Chitra if the month is Chaitra etc. The Mahabharata researchers like Shri. Oak and Shri. Achar routinely place moon in that nakshatra on Purnima day and calculate on that basis. Conversely if moon is in Jyeshtha on purnima day, the month must be Jyeshth, is the conclusion!
Out of curiosity I checked the position from Kalanirnay for all months of 2014 and found the rule is mismatched quite often! The table below shows the position for 2014. It can be seen that for 6 out of 12 months there is a mismatch!
Date of Purnima Month Name Nakshatra of the day
January 16 Poush Punarvasu NM
February 14 Magh Ashlesha NM
March 16 Falgun Purva-Falguni M
April 15 Chaitra Chitra M
May 14 Vaishakh Swati NM
June 13 Jyeshtha Jyeshthaa M
July 12 Ashadh Purvashadha M
August 10 Shraavan Shravan M
September 9 Bhadrapad Purva-Bhadrapada M
October 8 Ashvin Uttara-Bhadrapada NM
November 6 Kartik Ashvini NM
December 6 Margashirsha Rohini M
This is the position with the current accurate system of taking adhika masas. I wanted to see the position in Mahabharat days, with 2 Adhika masas together, after 58 continuous normally named masas –the Bhishma system. Shri. Oak generously helped to make a list of almost 100 consecutive months, and the purnima nakshatra of each in 2007 onwards from old Kalanirnay calendars. Then in the table, I named month nos 1 and 2 as Adhika and arbitrarily gave a name to month no.3 correctly matching the purnima nakshatra and then named 57 subsequent months as per normal sequence of Chaitra-Vaishakh etc. and then named the 59th and 60th months (month numbers 61 and 62) as Adhika masa, to resume normal names thereafter. So to say, I duplicated the Bhishma system. I found that by the time we go to 30th month onwards the month name and purnima nakshatra dont match at all and the mismatch kept on growing. It grew to 3 Nakshatras by 57th-58th month!
Month Number and Date of Purnima... Nakshatra ......Name of Month
1 ....................... 3-Jan-07 .......................Ardra-Punarvasu ........Adhika 1
2 ....................... 2-Feb-07 .......................Ashlesha .....................Adhika 2
3 ....................... 3-Mar-07 .......................Pur. Falguni ............ Falgun
4 ....................... 2-Apr-07 ........................Hasta ................... Chaitra
5 ....................... 2-May-07 ....................... Swati ....................Vaishakh
6........................ 31-May-07 ....................... Jyeshtha..................Jyeshth
7....................... 30-Jun-07 ....................... Pur Ash-Uttar ash.......... Ashadh
8 ...................... 30-Jul-07 ....................... Dhanishtha ................Shravan
9 ...................... 28-Aug-07 ....................... Shata-Pur Bhad.............Bhadrapad
10...................... 27-Sep-07 ....................... Uttara-Bhadra............. Ashvin
11 ..................... 26-Oct-07 ....................... Revati-Ashvini.............Kartik
12...................... 24-Nov-07......................... Krittika ................. Margashirsh
13...................... 24-Dec-07 ........................ Ardra..................... Poush
14...................... 22-Jan-08 ........................ Pushya.................... Magha
15 ......................21-Feb-08 ........................ Magha .................... Falgun
16 .......................................................................................... Chaitra
17............................................................................................ Vaishakh
18............................................................................................ Jyeshtha
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56....................... 15-Jun-11 ....................... Moola .................... Shravan
57....................... 15-Jul-11 ....................... Ut. Ash.-Shravan..........Bhadrapad
58 .......................11-Aug-11........................ Dhanishtha-Shata...........Ashvin
59 .......................12-Sep-11....................... Purva Bhadrapada .........Kartik
60........................12-Oct-11....................... Utt. Bhadr.-Revati........Margashirsh
61........................11-Nov-11....................... Bharani...................Adhika 1
62........................10-Dec-11........................ Mrugashirsha..............Adhika 2
(Details of intermediate months not filled in)
I conclude that the assumption which researchers routinely make about purnima nakshatra and month name matching, is not at all tenable for Mahabharat or such ancient time!