The first thing, the Mahadasha is calculated as per the fixed star the moon is situated near at the time of birth. Since Vedic technology is more than 2000 years old and the constellations have shifted relative to earth, you would have to check the placement of the fixed star closest to the degree of the moon at the time of birth And as the stars move relative to us, they're moving slowly, relative to the natal degree of the moon. To simplify, it can seem like the moon is progressing through the stars. Each star has a natural owner, a planet, whose energy it seems to embody. The period the moon seems to be in the vicinity of that planet becomes the Mahadasha of that planet. For example, my natal moon was at 12 degree 27 as per western astrology. You need to look at the Tropical Astrological Chart. As we can see, the stars are moving forward, so it'll seem like the natal moon point is moving backwards through them. And my moon is moving towards Arcus and Mimosa, and then Khamba...
One man's journey towards the truth.