Calculation methods and limitations

Our astrology calculators are early releases for exploring traditional methods. This page explains their current assumptions and limits. We are still checking the calculations against independent references, so results near a sign, star, or period boundary are provisional.

Jathakam

The Jathakam tool shows a sidereal birth-chart summary, including Rashi, Nakshatra, Pada, Lagna, graha positions, D1 whole-sign houses and a Navamsa D9 sign table. The D9 table divides each sidereal sign into nine equal parts and derives its Navamsa signs from those divisions; displayed D9 houses count inclusively from the calculated D9 Lagna. This V1 uses a Lahiri mean-ayanamsa reference adjusted by nutation in longitude for the true ecliptic of date, whole-sign houses and a mean lunar node. Calculations run in the browser. Independent spot checks against Swiss Ephemeris agree closely on recent and mid-twentieth-century examples. Moon longitude drift increases on distant future dates in a local 1800–2200 benchmark, reaching about 63 arcseconds by 2099 and about 142 arcseconds by 2199 in selected samples; these figures are limited samples, not guaranteed error bounds. The full range of dates, places and boundary cases has not passed independent validation.

Dasha

The Dasha tool derives a Vimshottari timeline from the calculated Moon position and uses a 365.25-day year convention. The first Mahadasha and its visible Antardasha rows begin at birth; a subperiod that was already running is shown only from birth, while the internal theoretical boundaries are retained to derive deeper periods. Timeline dates display in UTC. Different year-length and date-boundary conventions can produce different start and end dates. Treat these dates as provisional while the engine and period rules are checked.

Birth time and place

• Enter the clock time and the UTC offset that applied at the birthplace on the birth date. In Advanced settings you may enter a manual UTC offset or select a named IANA time zone. Named-zone mode uses your browser’s historical time-zone data for the entered date and place; a clock gap is rejected and a repeated time requires an explicit earlier/later choice. Confirm unusual historical records independently.
• The Kerala directory contains 1,666 revenue-village names across 14 districts and 78 taluks. A directory selection may use an approximate taluk-centre coordinate; confirm the exact hospital or birthplace on a map and enter its latitude and longitude in Advanced settings when precision matters.
• “Use my current location” reads the device’s present location only if the browser grants permission. It is not evidence of where someone was born.
• If the birth time or location is uncertain, Lagna and other boundary-sensitive outputs may change. Recheck the input before using a result.

Daily Panchangam and timings

The Panchangam calculates local sunrise, sunset, weekday, Moonrise and Moonset, and the Tithi, Nakshatra, Yoga and Karana present at sunrise, then their transitions through the next sunrise. Moon events are searched within the selected sunrise-to-next-sunrise interval; either event can be absent within that interval. Times round to the nearest minute. In named-zone mode, local day boundaries are resolved separately and each event is displayed using its applicable offset, including daylight-saving changes. Manual mode uses the entered fixed offset. Tithi divides Sun–Moon elongation into 12°; Karana divides it into 6°; Nakshatra divides the sidereal Moon circle into 27; Yoga divides the sum of sidereal Sun and Moon longitudes into 27. These definitions follow the IMD Positional Astronomy Centre explanation. Astronomy Engine 2.1.19 computes the solar rise/set and planetary positions; the sidereal transformation uses our Lahiri reference model with nutation adjustment; broad boundary validation remains open. A few 2026 Kochi transitions were checked against IMD tables, often at the displayed minute or within one minute. Eight Sun and Moon rise/set events at two Kerala locations on 28 September 2026 differed by about 0.2 minute from an independent Swiss Ephemeris calculation under comparable assumptions. Almanacs may use different rise/set conventions or inputs; these samples are not a general precision guarantee.

Daily Timings divides the interval from calculated local sunrise to sunset into eight equal parts. Rahu Kalam selects the Sunday-to-Saturday parts 8, 2, 7, 5, 6, 4, 3; Yamagandam parts 5, 4, 3, 2, 1, 7, 6; and Gulika Kalam parts 7, 6, 5, 4, 3, 2, 1. A Kochi example was compared with an independent calendar within about one minute. Solar results assume sea-level observer height and standard refraction. Terrain and atmosphere may shift actual sunrise/sunset. The tool accepts locations only between latitudes 65° S and 65° N and supports either a manual fixed UTC offset or event-specific named-zone formatting. It does not determine a complete Muhurtham.

Transit and birth-star tools

Gochara computes geocentric sidereal graha positions at the selected instant with the same approximate Lahiri reference and a mean lunar node. Sade Sati checks whether Saturn is in the 12th, first or second sign counted from the birth Moon sign; it also lists approximate future Saturn sign-boundary dates and phase changes, including retrograde returns, for up to 31 years. Independent sampled ingress comparisons varied by up to about an hour, so the page shows local dates rather than exact clock times; a near-midnight difference can change the date. It makes no personal prediction. Chandrashtama checks whether the selected instant’s Moon is in the eighth sign counted inclusively from the birth Moon sign and shows the approximate current or next eighth-sign interval. Four sampled Moon sign boundaries differed by roughly 3–7 seconds from an independent Swiss sidereal calculation under the chosen model, not a general error bound. These are sign-based checks, not whole-day or personal-outcome claims.

Tarabalam counts the transit Moon’s Nakshatra inclusively from the birth Moon Nakshatra, wraps across 27 stars and repeats nine positions: Janma, Sampat, Vipat, Kshema, Pratyari, Sadhaka, Naidhana, Mitra and Parama Mitra. It shows the actual count and named position, not a complete Muhurtham decision. The Moon can cross a star boundary within one date. Birth and transit forms accept separate manual UTC offsets or named IANA time zones. Named mode resolves each entered local instant using browser historical time-zone data; gaps are rejected and repeated times require an explicit choice. Near sign or Nakshatra boundaries, results are provisional until broader independent ephemeris comparisons are complete.

Porutham birth-star pair

The Porutham birth-star pair tool accepts two selected Nakshatra names, counts inclusively in both directions around 27 stars and checks the explicit Vedha pairs in a published Kerala matching discussion. It includes the mutually paired Mrigashira, Chitra and Dhanishtha group described there. It separately displays the paper’s ten named categories: Rasi, Rasiadhipa, Mahendra, Vasya, Gana, Yoni, Dina, Sthree Deergha, Rajju and Vedha. Rasi, Rasiadhipa and Vasya require both verified Padas because a birth star can cross a Moon-sign boundary. Some categories display source-specific counts or classifications instead of a final pass/fail judgment. An optional browser calculation derives each birth Moon star and Pada from date, local time and historical UTC offset using the site’s approximate sidereal model; it refuses positions within three arcminutes of a Pada boundary. It does not compute a complete horoscope match or produce a compatibility score. A separate Dasa Sandhi explorer compares major-period dates. Kerala rule variants differ, and a single pair check cannot recommend or reject a relationship.

Mahendra is shown as a directional inclusive star count in the 4, 7, 10 families and their nine-star repetitions. Dina shows the corresponding position within a nine-star group and flags the paper’s 3, 5 and 7 positions without claiming to resolve its regional exceptions. The Yoni labels are the paper’s M/F star categories, not a person’s sex or an animal-Yoni method. Rasiadhipa displays the derived sign rulers and the specific friendship list cited by this paper; Vasya lists its directed sign pairs. These historical categories do not predict children, sexual compatibility or relationship success.

For Sthree Deergha, the cited discussion counts inclusively from the woman’s birth star to the man’s and describes a count above 15. The tool states that role assumption, shows the count in both directions and labels whether each direction crosses the paper’s threshold. This is one historical factor, not a marriage recommendation.

The same paper supplies a 27-star Gana table with Deva, Manushya and Rakshasa labels. The tool shows each selected star’s label and whether the labels match, without applying the paper’s gender-specific judgments or turning a label into a relationship verdict. Different regional matching traditions and exceptions require further review.

The same cited paper also lists a five-section Rajju classification: Head, Neck, Stomach, Thigh and Feet. The Porutham tool displays each selected star’s section and whether the sections match. The paper separately describes a three-finger Rajju method used in parts of Kerala; the two classifications must not be treated as interchangeable. The tool does not apply a marriage verdict from either classification or reconcile local exceptions.

Chandrabalam sign count

The Chandrabalam tool counts the transit Moon sign inclusively from the birth Moon sign at the entered instant. The cited Drik Panchang Chandrabalam table labels counts 1, 3, 6, 7, 10 and 11 “Good”; 2, 5 and 9 “Puja Needed”; and 4, 8 and 12 “Bad”. The site repeats those source labels as a classification, not as a personal prediction or complete Muhurtham. The next sign-change time uses the approximate V1 Lahiri model and the selected transit time-zone method. Check exact time and location near boundaries and account for historical daylight-saving rules.

Limited Muhurtham Explorer

The Muhurtham Explorer compares the event venue’s local sunrise, sunset, sunrise-to-sunrise Panchangam transitions and weekday eighths for Rahu Kalam, Yamagandam and Gulika Kalam. Its Abhijit reference is the eighth of fifteen equal daylight parts, as described by Drik Panchang; that source gives Wednesday, marriage and Upanayana exceptions. These intervals do not by themselves select an auspicious time.

The optional Griha Pravesham check compares the Moon Nakshatra at the entered local event time with one published eight-star list. It also shows daylight segments when a listed star is present outside Rahu Kalam, using eight equal sunrise-to-sunset parts. The cited Griha Pravesh calendar excludes Sunday and Tuesday; those weekdays are excluded from displayed daylight reference intervals, and an entered event instant shows its Tithi for inspection without classifying it. These are limited screening factors, not approved ceremony times; Tithi suitability, lunar-month and regional checks are not applied, so there is no complete housewarming verdict. In named-zone mode, the seven-day table resolves each civil date and event time separately and formats transitions using the offset applicable to each instant, including daylight-saving changes. Manual mode holds the entered offset fixed across the range. Sunrise snapshots do not cover a whole day. The Moon-based transition times use the approximate V1 sidereal conversion and require independent confirmation near boundaries. The tool asks for a separate event venue from the birthplace, and optional Tara/Chandra factors are named counts rather than a date ranking.

Papasamyam placement explorer

The Papasamyam explorer accepts the sidereal signs of Lagna, Moon, Venus, Sun, Mars, Saturn, Rahu and Ketu for two charts. It counts whole-sign houses inclusively and lists placements of five grahas in houses 2, 4, 7, 8 and 12 from each of Lagna, Moon and Venus. It can optionally fill these signs from separately entered birth date, local time, UTC offset and coordinates for each chart using the site’s approximate sidereal model. It stops within three arcminutes of a sign cusp; confirm boundary positions independently. It additionally shows a seventh-house positional tally from one published Kerala method (pp. 38–39): each selected graha in the seventh from Lagna contributes 1, from Moon ½, and from Venus ¼. Eighth-house placements are displayed separately because that source adds them for a role-specific chart; the page neither assigns a gendered role nor combines the extra with the shared tally. Another rule discussion describes different graha and house variants. The tally omits dignity, benefic aspects, cancellation and other exceptions and is not a dosha score or marriage verdict. Confirm signs near cusps independently. The form operates in the browser and stores no entries on this page.

Dasa Sandhi comparison

The Dasa Sandhi explorer calculates each person’s Moon-based Vimshottari Mahadasha changes from their birth date, time and historical UTC offset using the same approximate sidereal and 365.25-day year conventions described above. Each chart accepts its own manual UTC offset or named IANA time zone, with explicit handling of clock gaps and repeated times. It lists pairs of transitions during the first 25 calendar years from an entered marriage date that fall within a 183-day screening threshold. A published Kerala matching discussion mentions transitions within six months and excludes transitions after 25 years, but disputes the weight given to this factor. The chosen 183 days is an approximation to six months, and day/year and ayanamsa conventions affect exact boundaries. It offers a date comparison, not a verdict. Entries stay in the browser on this page.

How to use the results

Astrological interpretations describe traditional beliefs, not scientifically established predictions. Do not use a chart or period date as the sole basis for medical, financial, legal or relationship decisions. We will revise the calculation notes as the reference tests and methodology review progress.