Mahabharata Vana-Parva 200:124-126 states..
पर्वसु द्विगुणं दानमृतौ दशगुणं भवेत
अयने विषुवे चैव षडशीतिमुखेषु च
चंद्रसुर्योपरागे च दत्तमक्षयमुच्यते
ऋतुषु दशगुणं वदन्ति दत्तं
भवति सहस्रगुणं दिनस्य राहो –
र्विषुवति चाक्षयमश्नुते फलं
(Dana (gifts/donations) given at the time of eclipses earns twofold piety and Dana given at the time of solstices and equinoxes earns ten fold piety. Dana given at the time of lunar or solar eclipses and also during the cardinal points of षडशीति is of a permanent kind.)
(Learned state that ‘dana’ given, at the time of the beginning of a season earns tenfold piety, at the time of solstices earn hundredfold piety, at the time of eclipses earn thousandfold piety and doing ‘dana’ at the time of equinoxes ensures sustenance of thie accumulated piety)
The meaning is straighforward except for the word षडशीति.
Per my timeline of Mahabharata, this conversation took place sometime during 5574 BCE – 5563 BCE, i.e. during first 12 years of Panadva brothers in Vana-vas.
We have to tap into सूर्य सिद्धांत – मनध्याय (Surya Siddhanta, Manadhyaya -Chapter 14:4-5) to eluciate the meaning of षडशीति.
तुलादे: षडशीत्यंशै: षडशीतिमुखं दिनं
भचतुष्टयमेवं स्याद द्विस्वभावेषु राशिषु
षडविंशे धनुषो भागे द्वाविंशेsतिमिनस्य च
मिथुनेs ष्टादशे भागे कन्यायां च चतुर्दशे
(षडशीति refes to a combination where/when cardinal points (solstices and equinoxes) are situated in the following four zodiacs -Sagittarius, Pisces, Gemini & Virgo).
While Surya Siddhanta refernce does not specify pairing of equinoxes/solstices with specific zodiacs, fortunately, this would not pose a problem in interpreting the reference in the context of Mahabharata timing.
Our objective is to identify a time interval, begining with the present, and going backwards until the time, when 4 cardinal points fall in the zones of 4 zodiacs of षडशीति, viz. Sagittarius, Pisces, Gemini & Virgo.
Step – 1
In our times, i.e. beginning with the present (2015 CE), we have a scenario that would qualify as षडशीति. If we simulate the skies (Voyager 4.5) going backwards, the scenario would last for 2000 years.
Researchers claiming the timing for Mahabharata, during last 2000 years, may employ this reference of Vanaparva as corroborative reference for their timeline.
I am not aware of any researcher claiming the occurrance of Mahabharata during last 2000 years. At least not the sensible kind.
We can discard this time interval, unless of course someone is going to make a case for ‘interpolation of this Vana Parva reference during last 2000 years’.
Step – 2
The point of Spring equinox was in the area of Zodiac Gemini from 4500 BCE through 6500 BCE.
The point of Summer solstice was in the area of Zodiac Virgo from 4000 BCE through 7000 BCE.
The point of Fall eqinox was in the area of Zodiac Sagittarius from 4000 BCE through 6500 BCE.
The point of Winter solsice was in the area of Pisces from 4000 BCE through 6500 BCE.
This analysis then provides us – 4500 BCE – 6500 BCE – as the time interval, beyond 2000 years of our recent past (by beginning with about 12 BCE and going back in antiquity) that qualifies matching of cardinal points with zodiac combination of षडशीति (a combination described in Vanaparva of Mahabharata, while the meaning of it (षडशीति), elucidated in Surya Siddhanta).
5561 BCE, the year of Mahabharata War, indeed falls in this time interval.
Critical readers and researchers would also notice that the time interval, so defined, by Vanaparva reference of षडशीति (4500 BCE -6500 BCE) matches the time interval (4500 BCE -6500 BCE), so defined, by combining outcome of AV observation (4508 BCE – 11091 BCE) with that of Bhishma Nirvana (4000 BCE – 6500 BCE) (refer to Figure 12 – Compressed Time Interval, in my book).