Indian chronology is genuinely contested. The ranges below are the honest ones; where scholars disagree, that is said rather than smoothed over.

Date	Event	Note
c. 1500–1200 BCE	Rigvedic star references	The Rigveda names stars and lunar stations in passing (the Krittikas, Tishya) but has no twelve-sign zodiac. Even the samhita's own date is disputed.
c. 1200–900 BCE	Nakshatra lists in the Yajurveda and Atharvaveda	The Taittiriya Samhita and the Nakshatra Sukta of the Atharvaveda give ordered lists of the lunar mansions — 27, or 28 with Abhijit. This is the older Indian sky-division, attested centuries before the rashis.
c. 1400–1200 BCE	Observations underlying the Vedanga Jyotisha	The solstice and nakshatra positions in the text fit this window. The inference is standard but not universally accepted.
c. 700–500 BCE	Vedanga Jyotisha of Lagadha compiled	The earliest surviving Indian astronomical text, in two recensions (Rig and Yajur). It computes a five-year luni-solar yuga to time sacrifices. It still has no rashis.
c. 2nd–3rd c. CE	Yavanajataka and Greek transmission	The Hellenistic twelve-sign horoscopic zodiac enters Sanskrit. David Pingree's 1978 edition dated Sphujidhvaja's verse redaction to 269/270 CE and posited a lost Greek prose original translated at Ujjain in 149/150 CE. Disputed: Bill Mak's 2013 study of a newly available Nepalese manuscript rejected Pingree's readings and his dating. Treat the century as unsettled; the Greek loanwords in the text are not.
499 CE	Aryabhata's Aryabhatiya	Dated by its own statement that the author was twenty-three, 3,600 years into the Kali Yuga. It gives the mathematical machinery — sines, planetary periods, a rotating Earth — on which later rashi computation runs.
6th c. CE	Varahamihira	The Brihat Jataka becomes the standard textbook of natal astrology and the Brihat Samhita the great compendium of omens, architecture and natural science. His Pancha-siddhantika summarises five earlier astronomical schools, which is how we know they existed.
c. 4th–10th c. CE	Surya Siddhanta	An older version is already being summarised by Varahamihira; the received text is usually placed several centuries later. The range is wide and contested.
8th–16th c. CE	The commentarial tradition	Kalyanavarma's Saravali, Bhattotpala's commentary on the Brihat Jataka (966 CE), the Brihat Parashara Hora Shastra (ascribed to the sage Parashara; its actual date is unknown and probably medieval), and the Phaladeepika.
1501 CE	Nilakantha Somayaji's Tantrasangraha	The Kerala school refines planetary models well before European contact.
1724–1735	Jai Singh II's Jantar Mantar observatories	Masonry instruments at Jaipur, Delhi, Ujjain, Varanasi and Mathura, built to correct the tables.
1955	Calendar Reform Committee	The committee under Meghnad Saha adopted the Lahiri (Chitrapaksha) ayanamsa as India's national standard for sidereal and religious calculation. The Indian National Calendar took effect on 22 March 1957.

Ayanamsa is the running gap between the tropical zero point (the March equinox) and the sidereal zero point. Because the equinox precesses westward along the ecliptic at roughly 50 arcseconds a year, that gap grows.

The Lahiri ayanamsa fixes the sidereal zodiac so that the star Chitra (Spica) sits at 180°, which puts the two zodiacs in agreement around the third century CE and about 24 degrees apart in the 2020s. Practically, that is why the Vedic sun sign is normally one sign behind the Western one: the Sun enters sidereal Mesha around 14 April, not 21 March.

The choice of ayanamsa is contested, and the disagreement is not trivial — a degree of ayanamsa moves every sign boundary by a day. Lahiri is the Indian government standard and the most widely used. Raman, after B. V. Raman, runs roughly a degree lower. Krishnamurti (KP) sits a few arcminutes from Lahiri. Others place the zero point at Revati or at a chosen fixed star. There is no neutral arbiter; each school defends its own.

Jyotisha is living Hindu religious practice, and is used across Hindu, Jain and some Buddhist communities. Its planets are the Navagraha — Surya, Chandra, Mangala, Budha, Brihaspati, Shukra, Shani, and the two shadow-grahas Rahu and Ketu, the lunar nodes. They are not abstractions but deities with iconography, weekdays, mantras and temples: a Navagraha shrine, nine figures set in a grid with Surya at the centre, stands in most South Indian temples and is circumambulated in its own right, and the Navagraha Sthalas around Kumbakonam are a pilgrimage circuit of nine temples, one per graha.

When a chart shows an afflicted graha, the classical remedies are graha shanti: japa of that graha's Vedic mantra, homa, fasting on its weekday, and dana — donation of its grain, metal, cloth and colour. Gemstone prescription is widespread today but belongs to later popular practice rather than the oldest texts.

The rashis touch ordinary life mainly through muhurta, the election of auspicious time, and through the samskaras. A horoscope is cast at birth; the first syllable of the child's name at Namakarana is taken from the pada of the Moon's nakshatra; Annaprashana, Chudakarana, Upanayana and Griha Pravesha are all timed by it. In Vivaha, marriage matching by kuta points scores eight factors out of thirty-six — Varna, Vashya, Tara, Yoni, Graha Maitri, Gana, Bhakut and Nadi — with the Bhakut kuta read from the two rashis and the Nadi kuta from the nakshatras. This is described here as belief and practice, which is what it is for a very large number of people.

One honest caveat: in Jyotisha the sign that matters most is usually the Janma Rashi, the Moon's sign at birth, or the Lagna, the rising sign. A solar sign of the kind this site displays is a Western habit applied to Indian data.

#	Rashi	Devanagari	Site dates	Ruling graha	Element	Quality	Tropical
1	Mesha	मेष	14 Apr – 14 May	Mangala	Agni	Chara	Aries
2	Vrishabha	वृषभ	15 May – 14 Jun	Shukra	Prithvi	Sthira	Taurus
3	Mithuna	मिथुन	15 Jun – 15 Jul	Budha	Vayu	Dvisvabhava	Gemini
4	Karka	कर्क	16 Jul – 16 Aug	Chandra	Jala	Chara	Cancer (Zodiac Sign)
5	Simha	सिंह	17 Aug – 16 Sep	Surya	Agni	Sthira	Leo
6	Kanya	कन्या	17 Sep – 16 Oct	Budha	Prithvi	Dvisvabhava	Virgo
7	Tula	तुला	17 Oct – 15 Nov	Shukra	Vayu	Chara	Libra
8	Vrischika	वृश्चिक	16 Nov – 15 Dec	Mangala	Jala	Sthira	Scorpio
9	Dhanu	धनु	16 Dec – 13 Jan	Brihaspati	Agni	Dvisvabhava	Sagittarius
10	Makara	मकर	14 Jan – 12 Feb	Shani	Prithvi	Chara	Capricorn
11	Kumbha	कुम्भ	13 Feb – 13 Mar	Shani	Vayu	Sthira	Aquarius
12	Meena	मीन	14 Mar – 13 Apr	Brihaspati	Jala	Dvisvabhava	Pisces

Each nakshatra spans 13°20′ and divides into four padas of 3°20′. Two and a quarter nakshatras — nine padas — fit inside each rashi, which is why so many nakshatras straddle a sign boundary. The presiding deities are Vedic; the ruling grahas are the lords of the Vimshottari dasha cycle.

#	Nakshatra	Sidereal span	Rashi	Presiding deity	Graha
1	Ashwini	0°00′–13°20′	Mesha	Ashvini Kumaras	Ketu
2	Bharani	13°20′–26°40′	Mesha	Yama	Shukra
3	Krittika	26°40′–40°00′	Mesha / Vrishabha	Agni	Surya
4	Rohini	40°00′–53°20′	Vrishabha	Prajapati	Chandra
5	Mrigashira	53°20′–66°40′	Vrishabha / Mithuna	Soma	Mangala
6	Ardra	66°40′–80°00′	Mithuna	Rudra	Rahu
7	Punarvasu	80°00′–93°20′	Mithuna / Karka	Aditi	Brihaspati
8	Pushya	93°20′–106°40′	Karka	Brihaspati	Shani
9	Ashlesha	106°40′–120°00′	Karka	the Nagas	Budha
10	Magha	120°00′–133°20′	Simha	the Pitrs	Ketu
11	Purva Phalguni	133°20′–146°40′	Simha	Bhaga	Shukra
12	Uttara Phalguni	146°40′–160°00′	Simha / Kanya	Aryaman	Surya
13	Hasta	160°00′–173°20′	Kanya	Savitr	Chandra
14	Chitra	173°20′–186°40′	Kanya / Tula	Tvashtr	Mangala
15	Swati	186°40′–200°00′	Tula	Vayu	Rahu
16	Vishakha	200°00′–213°20′	Tula / Vrischika	Indragni	Brihaspati
17	Anuradha	213°20′–226°40′	Vrischika	Mitra	Shani
18	Jyeshtha	226°40′–240°00′	Vrischika	Indra	Budha
19	Mula	240°00′–253°20′	Dhanu	Nirriti	Ketu
20	Purva Ashadha	253°20′–266°40′	Dhanu	Apas	Shukra
21	Uttara Ashadha	266°40′–280°00′	Dhanu / Makara	Vishvedevas	Surya
22	Shravana	280°00′–293°20′	Makara	Vishnu	Chandra
23	Dhanishta	293°20′–306°40′	Makara / Kumbha	the Vasus	Mangala
24	Shatabhisha	306°40′–320°00′	Kumbha	Varuna	Rahu
25	Purva Bhadrapada	320°00′–333°20′	Kumbha / Meena	Aja Ekapada	Brihaspati
26	Uttara Bhadrapada	333°20′–346°40′	Meena	Ahir Budhnya	Shani
27	Revati	346°40′–360°00′	Meena	Pushan	Budha

A twenty-eighth, Abhijit, appears in the older Vedic lists and is squeezed between Uttara Ashadha and Shravana. It is kept for muhurta and dropped from the even 27-fold division.

The breadcrumb bar picks the rashi from a fixed table of month-and-day boundaries. Those boundaries approximate the Lahiri sidereal ingress dates; they are not a live ephemeris, and the true sankranti can fall a day either side of the printed date and shifts slowly across centuries. Treat the chip as a cultural display of how a different sky-division names today — not as a computation you would use for ritual, and not as a claim that the sign predicts anything.

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