Maha Dasha is called after the Great period in a person's life. A particular stretch of time in an individual's lifespan is ruled by a particular planet. This time period is known as the Vimshottari Mahadasha of that planet. A particular sequence of planets is followed for their Mahadashas.
The total time span of these planets adds up to be 120 years. So it is highly unlikely that any person will repeat his Maha Dashas. Out of many Dasha systems, this is a follow up of Vimshottari Dasha system. This Dasha system works on the basis of Nakshatras. The start period of a particular Mahadasha at the birth of the individual will be based on the planet ruling the birth constellations, or JanmaNakshatra.
Each Nakshatra / constellation has a lord, one of the planets. The first dasha (period) is determined by the Nakshatra that the Moon is tenanting at the time of birth. For example, if the Moon is in the Nakshatra Anuradha, the order of the Mahadashas are Saturn, Mercury, Ketu, Venus, Sun, Moon, Mars, Rahu and Jupiter. The calculation begins with Saturn, because Saturn rules Anuradha. How long the first major period lasts is determined by how far the Moon has moved through the particular constellation it is tenanting at the time of birth.
Different MahaDasha influence different aspects in our life ruled by that planet. What effects a particular planet will exert in one's life are entirely dependent on that planets position in the horoscope along with an overall reading. Still, the aspects that will get affected are the ones governed by the planet. Whether the effects will be for good or bad is based on an individual's horoscope and the person's Free will. The areas in life affected (in general) by corresponding planets are:
Sun will govern high position in career, achievements especially in the Areas of politics and government. It adds on to charm and magnetism to our persona. It governs Fame, authority and advancement in careers. The sun Mahadasha also relates to our Father. If it's placed well, it will give highly auspicious results. In case Sun is badly placed, it will affect the above-mentioned fields in adverse ways. It can also create problems related to our heart and eyesight.
Moon Mahadasha :
Moon rules our emotions, thinking, general well-being and feminine presence in our chart. Hence, all theses areas are likely to come in limelight in this Dasha period of 10 years. If placed well, this period (in general) will give a physical well being along with mental peace and emotional richness. The females related to the subject will also receive added benefits from this period. Emotions, sensitivity, romance and marriage will gain prominence along with all the fields close to a subject's hearts. Public recognition and honor is also facilitated. In case the moon is not so well placed, the related fields suffer a setback. The problems of insomnia, lethargy, cough and cold, spleen and gastric disorders also come into play from the ill placement of the planet.
Mars Dasha is the time for passions and drives taking the front place. In a well-placed powerful Mars, the person becomes ambitious and independent. Sexual urges and excitement also comes in play. Since, Mars is a masculine planet, a subject's relationship with males, such as son and brothers are enhanced. This is perfect time to take charge of life and surge ahead with confidence. If the planet is afflicted in the chart, a person might get into occasional rash behaviour and will be prone to injuries and accidents. Bone marrow and muscles also get affected as an adverse result.
Rahu period usually brings out the best and worst in our fortunes and personal self. If badly placed, this planet will accordingly bring misery, conflicts, downfalls, difficulties and even death. If the planet is well placed then the person is bestowed with highest honors, achievements and success. In this period, the person doesn't exactly 'grow' but rather reap rewards of the earlier Dasha of his life. This dasha may also incline one to 'demonic' habits (such as alcohol, non vegetarism, drugs etc), as the planet itself is symbolic of a demon. The ill effects of this period may include_once leprosy, nervous disorders, ulcers and cancer. Jupiter Mahadasha:
Jupiter rules luck, fortune and higher wisdom. Hence all the related aspects are going to come in the foreplay during this period. When well placed, the period favours easygoing life with easy acquisition of properties, wealth, career advancement and children. Overall, the time period will be smooth and rewarding. A great deal of higher learning and spiritual inclination may also take place during this period. Prosperities and honors are acquired during this time period. If not so well placed, the planet gives bad effects in the above-mentioned areas. Disorders related to blood circulation and liver, asthma and diabetes can also cause major inconvenience. Saturn Mahadasha:
This is the 19 years time period of hard work and persistence. Saturn emphasizes on strict discipline and labour by creating delays and difficulties and added responsibilities on the person. In short, this time period enables a person to lay the foundation to become strong and efficient, and reap the rewards in coming years. If the Saturn is well placed, it brings honor, authority and prosperity as a result of one's work. In case it is afflicted, the time period brings major difficulties, sorrows and frustrations. Bone diseases, fractures, skin problems, rheumatism also come in the play as ill effects of the Dasha.
A Mercury Dasha stresses on all the intellectual endeavors. Learning, writing, speech and communications are the fields of this planet, which come in play during this time span. A person's education gains importance, and people deal more with the communication aspects in their life. Those active in the field of writing, media or telecommunication receive an added boost because of this dasha. If the planet is afflicted, mental tensions, anxiety, instability and indecisiveness are the back points that become evident. Commercial activities also gain prominence in this time period; hence loss in business is also attributed to ill placed Mercury.
Ketu is the planet of spiritual enlightenment and detachment from everything materialistic or worldly. In a materialistically inclined horoscope, Ketu may endow sorrows, losses and miseries. In a spiritually inclined horoscope, it may give great deal of spirituality and asterism to the person. Ketu gives good results when placed in proper houses imparting mystical and psychic experiences. Still, outcome of the period may be varied.
This 20-year time span revolves around beauty, luxuries, entertainment, romance and affairs of the heart. This time period associates the person with the above-mentioned activities. People active in fields of arts and entertainment are also liable to give wonderful results in this time period. Happiness and pleasantness becomes the life's core when this planet is well placed. If the planet is afflicted, romantic alliance, marriage and endeavors in above-mentioned activities will give bad results. Money loss is also prominent. Kidney and reproduction system may also suffer as the consequence of its bad effects.
Each MahaDasha of these nine planets are again divided into sub periods (Antardashas or bhuktis), again ruled by nine planets. For example, on the starting point of Maha Dasha of Budh, the dasha of Budh will start (Budh - Budh). Then the sub period of Ketu will start (Budh - Ketu). The sequence will get followed. Again each Dasha is divided into minor periods (Pratyantar dasha) to gain more accuracy in analyzing the timing of event in the individual's life.
Thus, the concept of the time zones of one's life leads to a closer study of ups downs and trends in a person's life. The effects of the planets are always there. The final outcome is ultimately in hands of the subject himself. One may have to fight against the times that are not so good, and cash in the times that are good to make the life complete and enriched. Understanding the Map of life is the half the battle won towards the goal of living the life of our desires.