Nava Nayaka calculation formulae based on transit of Sun, weekdays and Ugadi for each Vedic New Year (Vikrama and Salivahana saka).
Vedic Astrology calculates start of a new year from the day of Ugadi, which is first day of Chaitra month (usually occurs in March-April every year).
Ugadi predictions are mainly based on Nava Navayaka results. Just as an ancient kingdom is ruled by 9 nayaka (administrators), a vedic year is also administered by 7 planets, who get portfolios.
Rahu and Ketu are exempted from these 9 portfolios as they do not own a weekday or zodiac sign.
Even if first day (padyami or pratipada) of a month starts on a day after sunrise, that day is not counted but next day when same tithi (lunar day) at sunrise is taken into account.
One planet (graha) can get 1 or more portfolios, whereas few may not get any in a year.
Also in this year (Vikrama or Salivahana saka), Natural malefics (Sun, Mars, Saturn) getting more (atleast 5 out of 9) portfolios indicate administration and nature being tough on human beings for that year.
Natural benefics (Moon, Jupiter, Venus) getting more portfolios is good for general wellbeing.
Mercury is neutral planet and behaves according to conjunction(s) on ugadi day.
General administration is with the Prime Minister, so a natural administrators Aries (Mesha Rasi) and Sun are chosen.
Commander-in-chief (Senadhipathi) is chosen based on day when Sun enters Leo (Simha Rasi) because Leo is a natural commander.
In many tropical countries, cultivated crop is collected and sold during December-January each year. That is why Dhanyadhipathi (cereals and food grains) is chosen when Sun enters Sagittarius (mid-December each year).
Summer solstice (usually 21 June) is chosen as Meghadhipathi (clouds and rainfall) because that is when Moonsoon usually starts in India.
Similarly other portfolios are chosen based on weekdays when Sun enters respective zodiac signs (in that year).
Nava Nayaka Calculation method for Ugadi New Year
- King (Raja) : The day lord of Chaitra sudha Padyami/Pratipada (at sunrise)
- Mantri (Minister): The day lord when Sun enters Aries (Mesha Rasi)
- Senadhipati (Commander-in-Chief): The day lord when Sun enters Leo (Simha Rasi)
- Argyhadhipati (Water): The day lord when Sun enters Gemini (Mithuna Rasi)
- Meghadhipati (Clouds): The day lord when Sun enters Arudra Nakshatra
- Sasyadhipati (Agriculture): The day lord when Sun enters Cancer (Karkataka Rasi)
- Dhanyadhipati (cereals and grains): The day lord when Sun enters Sagittarius (Dhanu Rasi)
- Rasadhipati (beverages, defence etc): The day lord when Sun enters Libra (Thula Rasi)
- Neerasadhipathi (Diseases, relations, Karma etc): The day lord when Sun enters Capricorn (Makara Rasi)
Sometimes these Navanayakas vary for same year because of Ayanamsa or panchang-ganit method chosen by astrologers.
KP or its closest N.C.Lahiri ayanamsa (Drik siddhantha) are the most accurate methods to be used.