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Vimshottari Dasha — Calculating Periods
The dasha system as a concept is introduced in the Foundations section. This page covers the calculation mechanics — how the Moon's position at birth produces the dasha sequence, how the balance at birth is determined, and how the three levels of subdivision work mathematically.
Starting Point: The Moon's Nakshatra§
There are 27 nakshatras, each spanning 13°20' of the zodiac. Each nakshatra is assigned a dasha lord:
| # | Nakshatra | Lord | # | Nakshatra | Lord |
|---|---|---|---|---|---|
| 1 | Ashwini | Ke | 15 | Swati | Ra |
| 2 | Bharani | Ve | 16 | Vishakha | Ju |
| 3 | Krittika | Su | 17 | Anuradha | Sa |
| 4 | Rohini | Mo | 18 | Jyeshtha | Me |
| 5 | Mrigashira | Ma | 19 | Mula | Ke |
| 6 | Ardra | Ra | 20 | Purva Ashadha | Ve |
| 7 | Punarvasu | Ju | 21 | Uttara Ashadha | Su |
| 8 | Pushya | Sa | 22 | Shravana | Mo |
| 9 | Ashlesha | Me | 23 | Dhanishtha | Ma |
| 10 | Magha | Ke | 24 | Shatabhisha | Ra |
| 11 | Purva Phalguni | Ve | 25 | Purva Bhadra | Ju |
| 12 | Uttara Phalguni | Su | 26 | Uttara Bhadra | Sa |
| 13 | Hasta | Mo | 27 | Revati | Me |
| 14 | Chitra | Ma |
Computing the Birth Balance§
The Moon at birth is somewhere within its nakshatra. Its exact position determines how much of the opening dasha remains:
- Find the Moon's longitude in degrees (0–360°, sidereal)
- Determine which nakshatra it falls in: nakshatra number = floor(longitude / 13.333...) + 1
- Find the nakshatra's start longitude: (nakshatra number − 1) × 13.333...
- Compute degrees elapsed: Moon longitude − nakshatra start
- Fraction elapsed = degrees elapsed / 13.333...
- Balance remaining = (1 − fraction elapsed) × dasha years
If the Moon is at the beginning of its nakshatra, almost the full dasha remains. If it's near the end, only days or months are left.
The Antardasha Calculation§
Each mahadasha divides into 9 antardashas using the same nine planets in the same sequence, starting from the mahadasha lord itself. The duration of each antardasha is:
Antardasha years = (Mahadasha years × Antardasha lord's years) / 120
For example, during Venus mahadasha (20 years):
- Venus antardasha: (20 × 20) / 120 = 3 years 4 months
- Sun antardasha: (20 × 6) / 120 = 1 year
- Moon antardasha: (20 × 10) / 120 = 1 year 8 months
And so on for all nine planets. The total of all nine sub-periods within a mahadasha equals the mahadasha's full duration.
Pratyantar and Below§
Pratyantardasha (sub-sub-period) applies the same formula one level deeper: Pratyantar years = (Antardasha years × Pratyantar lord's years) / 120. A fourth level (sookshma) and even a fifth (prana) are defined in the texts but used primarily for extremely precise event timing by specialists.
Reading the Dasha Panel in Moonketu§
The dasha panel below every chart in Moonketu shows:
- The active Mahadasha and Antardasha with start/end dates, highlighted
- An accordion that expands to show all 9 Antardashas within the active Mahadasha
- Pratyantardashas within the active Antardasha
The active period is computed relative to the current date (Time.now.utc), so it reflects where things stand today — not at the time of birth.
The dasha calculation is deterministic: given an exact Moon longitude and a birth date/time, the full sequence of periods through 120 years can be computed precisely. The quality of each period is the interpretive question — and that requires reading the dasha lord's natal strength, house rulership, and relationship to the antardasha lord. See the dasha system for the foundational introduction, and Rahu and Ketu for how the nodes behave as dasha lords. Jaimini's sign-based parallel is Chara Dasha. See your active dasha period.