Dasha dates
Why dasha calculators disagree by days
A dasha date depends on the year length, the ayanamsa and the birth time. See one period’s start move by weeks between conventions for the same birth.
01 · One date, several conventions
Year length, ayanamsa and birth time each move a dasha date.
The dasha balance is a number of years. Turning it into a date needs a length of year, and finding it needs the Moon’s sidereal position, which depends on the ayanamsa and the birth time. Each choice moves the result.
Three inputs behind every date
The first Vimshottari period is shortened by a balance, the share of the Moon’s nakshatra still to be crossed at birth, as how the first dasha and its balance are found explains. Every later date follows from the birth time plus that balance plus whole periods. Three choices sit underneath:
- The Moon’s position, which depends on the ayanamsa, the offset used to turn a tropical longitude into a sidereal one, as why the ayanamsa matters at boundaries explains.
- The birth time, since the Moon moves about half an arcminute a minute.
- The length of a dasha year used to turn years into days.
One birth, seven answers
For the fictional chart of 17:05 IST on 1 November 2026 in Delhi, the site puts the start of Mercury’s major period on 10 April 2036. Changing one input at a time:
| Convention | Mercury begins | Shift |
|---|---|---|
| The site: True Chitrapaksha, 365.25-day year | 10 April 2036 | |
| Year of 365.2422 days, the tropical year | 10 April 2036 | same day |
| Year of 360 days | 21 February 2036 | 50 days earlier |
| Lahiri formula ayanamsa | 18 April 2036 | 8 days later |
| KP ayanamsa | 2 March 2036 | 39 days earlier |
| Birth five minutes earlier | 6 May 2036 | 25 days later |
| Birth five minutes later | 16 March 2036 | 25 days earlier |
The year length barely matters between 365.25 and 365.2422 days, but a 360-day year, used in some traditional reckonings, moves this date by seven weeks. The ayanamsa matters more than it looks: KP’s differs from the site’s by a few arcminutes, and each arcminute of the Moon is worth about nine days here.
Which to trust
None of these is an error; they are conventions, and a calculator should say which it uses. Two calculators that agree on all three usually agree to within a day. When two disagree by days or weeks, check the ayanamsa first, then the year length, then whether the same birth time and time zone were entered. The Vimshottari guide gives the site’s choices and how it marks periods that a birth-time uncertainty leaves unsettled.
Calculate a chart and change its ayanamsa on the Kundli page, or explore another topic in Learn.