Planet Transit Dates (Graha Gochar)

What a sign ingress is

The zodiac is divided into twelve rasis of thirty degrees each. A graha's ingress is the instant its longitude crosses one of those twelve boundaries. Nothing about the sky changes at that instant - the boundary is a convention of measurement - but it is the moment at which every rule reckoned by sign, from gochara to the dasha lords' placements, begins to read the graha in a new rasi.

These are sidereal (Nirayana) boundaries, measured from the fixed stars with the Lahiri ayanamsha, and they currently sit about 24 degrees behind the tropical boundaries a Western ephemeris uses. How far that moves a date depends entirely on how fast the graha travels, because the date is the moment it covers those 24 degrees: about a day and a half for the Moon, about twenty-four days for the Sun, roughly six weeks for Mars, close to ten months for Jupiter and about two years for Saturn. So a sidereal and a tropical table do not sit a few days apart on Guru gochar or Shani gochar - they name different years. Both are measuring the same sky; only the starting point differs.

How often each graha changes sign

The apparent speeds differ enormously, so the same table means something different for each row:

• Moon - about every 2.3 days, roughly 160 ingresses a year.
• Sun - once a month, on the sankranti; twelve a year, always in the same order.
• Mercury and Venus - about twelve a year each. Both accompany the Sun as seen from the Earth, so they circle the zodiac once a year, whatever their orbital periods around the Sun.
• Mars - about every two months, and much longer when it retrogrades inside a sign.
• Jupiter - about once a year; a full circuit takes just under twelve years.
• Saturn - about every two and a half years; a full circuit takes about 29.5 years.
• Rahu and Ketu - about every eighteen and a half months, and always backwards through the zodiac.

Why one transit can have three dates

A graha routinely crosses a boundary, turns retrograde a few weeks or months later, backs over the same boundary, and then crosses it again for good. Jupiter did this three years running: it entered Sagittarius on 29 March 2019, returned to Scorpio on 23 April, and re-entered Sagittarius on 5 November; the same pattern repeated into Capricorn in 2020 and into Aquarius in 2021, where the first contact of 6 April and the final crossing of 20 November are more than seven months apart. Saturn's longest reversal on record in this engine's range ran even longer: it entered Capricorn on 2 February 1961 and did not settle there until 8 October.

This is why published tables can appear to disagree with one another when they are all correct: one prints the first contact, another the final crossing. This page prints the final crossing as the transit date, because that is the moment from which the graha occupies the sign continuously, and it names the reversed contact on the same row so nothing is hidden. The same rule governs Sade Sati's start and end dates elsewhere on this site.

Rahu and Ketu move backwards, and there are two of them

The lunar nodes are not bodies but the two points where the Moon's path crosses the ecliptic, and they regress: Rahu's next sign is the one before its current one, not the one after. A node transit therefore runs Aries to Pisces to Aquarius, never the other way. Ketu is always exactly opposite Rahu, so the two change sign at the same instant, six signs apart.

There are also two defensible ways to compute them. The mean node regresses at a uniform rate and never reverses; the true node oscillates about the mean by up to a degree and a half, so its ingress can fall as much as a month away from the mean node's. Panchangs differ on which they tabulate. Both are computed here and the choice is offered rather than made silently, because correcting one into the other would be inventing agreement that the published tables do not have.

How the dates are computed, and the range they cover

Each date is found by scanning the graha's sidereal longitude and then bisecting the crossing to well under a second of time, so the printed minute is the real one rather than a rounded day. Positions are computed to sub-arcsecond precision. Times are Indian Standard Time; a crossing shortly before or after local midnight will therefore fall on a different calendar date in another timezone.

The range is 1801 to 2100, which is the span this engine answers at full precision. Dates outside it are refused outright rather than answered from a lower-precision model.