Dasha

Dasha (दशा) is a planetary period in the Jyotish and Sankhya Shastra (Vedic numerology) systems, setting the quality of the current phase of life through the activation of karmic potentials of the ruling Graha.

The core idea. A person's life is divided into segments, each ruled by one of the planets. When a planet "switches on", its themes, trials and opportunities are activated — the karma of the Graha becomes events.

Vimshottari Dasha

The most widespread system is the Vimshottari Dasha ("the one hundred and twenty years"): a full cycle of 9 planetary periods with a combined length of 120 years. The starting Dasha is determined by the position of the Moon in the Nakshatra at the moment of birth.

The 9 periods and their lengths:

• Surya (Sun) — 6 years
• Chandra (Moon) — 10 years
• Mangala (Mars) — 7 years
• Rahu (North Node) — 18 years
• Guru (Jupiter) — 16 years
• Shani (Saturn) — 19 years
• Budha (Mercury) — 17 years
• Ketu (South Node) — 7 years
• Shukra (Venus) — 20 years

Total: 120 years.

Sub-periods

Within each Maha Dasha there are sub-periods:

• Antardasha — a sub-period ruled by a different Graha
• Pratyantardasha — a sub-sub-period

Threefold rulership. Every moment of life ends up under threefold planetary rulership. Each Dasha activates the themes, qualities and challenges of its Graha — career, relational, spiritual — in accordance with its nature and position in the natal chart.

Comparison with Ba Zi

The structural analog in Ba Zi is Da Yun (#10), but the mechanism is fundamentally different:

• In Ba Zi the Da Yun length is always 10 years, in Vimshottari each period has a unique length
• The ontology also differs: Dasha is a planetary force (Graha), Da Yun is a temporal pillar of destiny (stem and branch)

In Sankhya Shastra, Dasha is used as a predictive layer on top of the numerical triad Jiva–Dharma–Karma.