Dasha Mahadasha is a timing system unique to Vedic Astrology. There are several Dasha System in Indian Astrology, the notable ones being Vimshottari, Kalachakra, Yogini, Ashtotri, Jaimini and Chara Dasha.Vimshottari Dasha is the most widely used and most important system for timing events in one’s life. Its accuracy in prediction is amazing once an astrologer fits the past events.
Vimshottari is a sanskrit word that means 120. According to this system, the maximum life span of a person is 120 years in a cycle. Each of the seven planets and the two lunar nodes (making the nine navagraha) has its own period or mahadasha in the cycle. The duration of the Mahadasha of each planet in years, the order of the Mahadashas and the three nakshatras for each of the starting mahadashas is given in the table here.
The order of the Mahadasha remains the same irrespective of the starting Mahadasha. If a person is born in Jupiter Mahadasha, the next will Saturn Mahadasha, followed by Mercury, Ketu, etc. If the first is Venus Mahadasha, the second will be Sun Mahadasha, third of Moon, so and so forth. The planet which rules the first Mahadasha is decided by the Janma Nakshatra or the birth-asterism. It is for this reason Vimshottri Mahadasha is also known as Nakshatra Dasha. Since there are 27 Nakshatras and nine planets, the ruling-period of a planet at birth corresponds to three Janma Nakshatras as shown in the table.
From the table we can easily determine the Mahadasha at birth. If a person is born in the Revati Nakshatra for example, he is born during the ruling-period of Mercury, because the planet corresponding to Revati is Mercury. Similarly if Janma Nakshatra is Hasta, the first Mahadasha is of Moon. Janma Nakshatra is easily determined from the Moon’s longitude and is usually recorded in the horoscope. The exact position of the moon in the janma nakshatra determines the proportion of the first mahadasha that there is to run. In other words, if the moon is 1/4 of the way through the nakshatra Punarvasu, then 1/4 of the time is taken from the first mahadasha, giving only 12 years (3/4) left for the Jupiter period to run. The person would thus come under the influence of the next mahadasha (Saturn) at only 12 years old, despite the Jupiter mahadasha normally lasting 16 years.
AntarDashas (Sub Ruling-Periods)
The long period of a Mahadasha is subdivided into smaller periods, known as Bhukti or Antardashas or ‘sub-ruling-periods’ which run in the same order as the mahadashas, and with the same proportional length. For example, the first bhukti of Ketu is Ketu/Ketu, the second is Ketu/Venus, the third Ketu/Sun and so on. This subdivision allows a much more detailed examination of the influence of each mahadasha, and a much clearer indication of what events are expected to occur and when.When a Mahadasha of a planet begins, Antar dasha of the same planet also begins.
To calculate the duration of the Antar dasha of a planet in the Maha dasha of another planet, first multiply the duration of both of the planets in years; then divide the product by 120. For example, the Antardasha of Sun during the Mahadasha of Sun will be 6×6/120=0.3 years, or 3 months 18 days. We divide the product by 120, because in the Vimshottri Dasha system the total number of years assigned to all planets is 120 years.
Similarly, Antardasha of Moon under the Mahadasha of Sun will be of 10×6/120=0.5 years or 6 months duration. For calculating any Antardasha in the Mahadasha of Sun, one can simplify the calculations by dividing the number of years of the planet by 20.
Pratyantar dashas (Minor Ruling-Periods)
The Antardashas are further divided into smaller periods known as Pratyantra dashas, and we can call them ‘minor ruling-periods’. The minor-periods follow the same order as the Mahadashas beginning with the planet of the Antardasha. To calculate the Pratyantardasha of a planet, take the Antardasha and multiply it with the number of years of the Maha dasha of the planet and divide the product by 120. For example, we know that the Antar dasha of Sun in Sun’s Maha dasha is of 3 months and 18 days or 108 days. To calculate the Pratyantar-dasha of Sun in this Antardasha, multiply 108 days with 6 and divide by 120, which is equal to 5 days and 9 hours. The minor period of Moon will be 108×10/120, or 9 days. Similarly you can calculate the other Pratyantardashas.
The Antar dasha of Moon in the Mahadasha of Sun is 6 months or 180 days. The Pratyantar dasha of Moon will be of 180×10/120 = 9 days. The minor period of Mars will be of 180×7/120 = 10 days and 12 hours. The Pratyantardasha of Rahu will be of 180×18/120 = 27 days. Similarly the Pratyantar dashas of other planets in the Antardasha of Moon in the major period of Sun can be calculated.
Further subdivision the Pratyantar dashas into still smaller periods are known as Sukshama Dashas and Prana Dashas and can be calculated by following the same procedure.