What is Vedic astrology?
Jyotiṣa in plain words — and exactly what we compute.
The idea, in one paragraph
Vedic astrology is called Jyotiṣa, roughly “the study of light.” It is India’s way of reading the sky you were born under, and it differs from the horoscope in a Western magazine in one large way: it looks at the Moon first, not the Sun.
Wherever the Moon stood at your first breath falls inside one of twenty-seven small patches of sky, and each patch has a name. That patch is your nakshatra. In this tradition it sits closer to “your sign” than anything the Sun is doing.
Why your sign isn’t the sign you already know
Western astrology measures the zodiac from the spring equinox: 0° Aries is wherever the Sun sits on the first day of spring. Jyotiṣa measures it from the stars themselves. The two starting points were once the same, but the Earth wobbles slowly on its axis, and over some seventeen centuries they have drifted about twenty-four degrees apart.
That gap has a name — the ayanāṃśa — and it is the entire reason a Moon that Western astrology files under Pisces is called Kumbha (Aquarius) in a Vedic chart. Neither answer is a mistake. They are two different rulers, and each tradition should say which ruler it is holding.
How Bokki calculates it
Three steps, and not one of them is a lookup in a table of pre-written answers.
First the Moon. We ask an ephemeris — the astronomy-engine library, good to about one arcminute — where the Moon actually was at your birth instant. Second the ayanāṃśa. We subtract the Lahiri (Chitrapakṣa) value, the one most Indian almanacs use, computed as 22.460148 + 1.396042·T + 0.000308·T², where T counts Julian centuries from 1900. That gives 23.856° at the start of 2000 and 24.220° at the start of 2026.
Third the division. The sidereal circle is cut into 27 nakshatras of 13°20′ each, and each nakshatra into four padas of 3°20′. Your rāśi — the Vedic Moon sign — is the 30° slice the same longitude lands in.
Swap the ayanāṃśa for another school’s and every one of those answers can move. So ours is pinned in the code, and written out here, so you can check us against your own pañcāṅga.
The clock inside your Moon
Jyotiṣa does not only ask what you are like. It asks when. The Vimśottarī daśā system hands a hundred and twenty years out to nine planets in a fixed order — Ketu 7, Venus 20, Sun 6, Moon 10, Mars 7, Rahu 18, Jupiter 16, Saturn 19, Mercury 17.
Which period you were born into is decided by your nakshatra. How much of it was left is decided by how far the Moon had already travelled through that nakshatra. A worked example straight out of our code: a Moon at 45° sidereal sits five degrees into Rohiṇī, so 8°20′ of its 13°20′ remain — 62.5% — and Rohiṇī belongs to the Moon, whose period runs ten years. Balance at birth: 6.25 years of a Moon daśā.
Each period is then cut into nine sub-periods (antardaśā) by the same proportions — mahādaśā years × sub-lord years ÷ 120 — and the nine add back up to the whole exactly. That sum is not a coincidence; it is the check that tells you the arithmetic is right.
One choice we had to make, so we wrote it down
A daśā is counted in years, and schools disagree about how long a year is. Modern Jyotiṣa software generally uses the Julian year of 365.25 days; some classical schools use a 360-day sāvana year. Across a nineteen-year Saturn period that is a gap of about a hundred days, and across the full 120-year cycle about 1.7 years.
Bokki uses 365.25 days. We are not saying the other school is wrong. We are saying that if you compare us against another calculator and the dates sit slightly apart, this is very likely why — and you deserve to know which convention produced the number on your screen.
What Bokki does not compute
This part runs longer than most sites would print, and that is deliberate. Bokki computes the Moon — nakshatra, pada, rāśi — and, if you give a birth time and pick a birthplace from our list, the lagna, the rising sign, which needs the true instant and your latitude.
It does not build a full kundli: the nine grahas are not placed in twelve houses. There are no divisional charts, so no navāṃśa (D-9). There are no yogas and no doṣas — no maṅgala doṣa, no sade sati verdict.
There is no aṣṭakūṭa guṇa milan, the thirty-six-point marriage matching, and there will not be. Putting a score on whether two people should marry is precisely the thing this project refuses to do. There is no muhūrta, and there are no remedies — no gemstone, no mantra, no ritual to buy. Those belong to a jyotiṣī and a lineage, not to a web page.
And a limit worth saying out loud: if you leave the birth time blank we read the Moon at noon. The Moon covers about thirteen degrees a day and a nakshatra is 13°20′ wide, so an unknown hour really can move you into the neighbouring nakshatra. If you give a time but no birthplace, we read that clock as UTC and say so on the screen. Pick your birthplace and we use the true instant instead. We would rather show you the seam than hide it.
Closing note — one worked Moon, 62.5% of a nakshatra, a 100-day school gap
In short: a rāśi is not looked up, it is computed three ways in sequence — an ephemeris gives the Moon's real position, the Lahiri polynomial (22.460148 + 1.396042·T + 0.000308·T²) subtracts a moving zero point that grew from 23.856° at the start of 2000 to 24.220° at the start of 2026, and the sidereal circle is cut into 27 nakshatras of 13°20′. Our own worked example: a Moon at 45° sidereal sits 5° into Rohiṇī, so 62.5% of that nakshatra remains, and because Rohiṇī belongs to the Moon, whose Vimśottarī period runs ten years, the balance at birth is 6.25 years of a Moon daśā — the nine sub-periods that follow add back to that exactly, which is the check that the arithmetic is right.
One choice we make rather than hide: a daśā year is 365.25 days here, not the 360-day sāvana year some classical schools use, a gap of about a hundred days across a nineteen-year Saturn period. And a long list stays uncomputed on purpose — houses, divisional charts, doṣas, and the 36-point guṇa milan that scores whether two people should marry, which is precisely what this project refuses to build.