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Jyotisha is a Vedanga, one of the six limbs of the Veda, and is called the eye of the Veda because no rite happens without a time chosen for it. Mithuna's contribution to that machinery is Budha, its lord: in the Puranas the son of Chandra and Tara, a graha of ambiguous parentage and quick intelligence, associated with Vishnu, given Wednesday as his day and green as his colour. His temple in the Navagraha circuit of the Kaveri delta is Thiruvenkadu, and he stands in the nine-planet shrine that most South Indian temples maintain — Surya at the centre, the eight others around him, each facing its own quarter, walked around in order. Remedies for an afflicted Budha follow the classical form: japa of his mantra, homa, a Wednesday observance, and dana of green gram, green cloth and bronze.

The nakshatras falling in Mithuna:

Nakshatra	Padas in Mithuna	Deity	Graha
Mrigashira	3–4	Soma, the moon-draught of the sacrifice	Mangala
Ardra	1–4	Rudra, the howler, the fierce form of Shiva	Rahu
Punarvasu	1–3	Aditi, mother of the Adityas	Brihaspati

The pairing of Rudra and Aditi in one sign is worth pausing on. Ardra is Tiruvathirai in the Tamil calendar, and Arudra Darshanam at Chidambaram — the night the Nataraja image is bathed and shown — is set by that nakshatra; it is one of the more intense Shaiva observances of the year. Aditi's Punarvasu, by contrast, is the mother of the twelve Adityas, the solar deities whose worship stands behind the Sun's place in the Navagraha. In muhurta, Ardra is generally avoided for auspicious beginnings and Punarvasu favoured for return, repair and re-starting. The naming syllables at Namakarana come from the Moon's nakshatra pada — Ku, Gha, Nga and Chha for Ardra; Ke, Ko and Ha for the first three padas of Punarvasu — and Annaprashana, Chudakarana and Upanayana are all elected by the same tables. In marriage matching, Mithuna is scored through the Bhakut kuta and its nakshatras through the Gana and Nadi kutas of the thirty-six-point system.

Date	Event	Note
c. 1200–900 BCE	Nakshatra lists in the Yajurveda and Atharvaveda	Mrigashira, Ardra and Punarvasu appear in the earliest ordered lists — the Indian sky-division that predates the rashis.
c. 700–500 BCE	Vedanga Jyotisha of Lagadha	Earliest surviving Indian astronomical text; the date range is disputed.
c. 2nd–3rd c. CE	Yavanajataka and Greek transmission	The twelve-sign zodiac arrives from Hellenistic astrology, twins and all. Pingree's 269/270 CE dating is disputed by Mak (2013).
499 CE	Aryabhata's Aryabhatiya	Sines and planetary periods; the arithmetic of the ingress.
6th c. CE	Varahamihira, Brihat Jataka and Brihat Samhita	Standard significations of Mithuna set down.
c. 4th–10th c. CE	Surya Siddhanta	Contested range.
~15 June, annually	Mithuna Sankranti	In Odisha this begins Raja Parba, three or four days on which the earth-goddess Bhudevi is held to menstruate: ploughing stops, the ground is left unturned, and women rest and swing. It is a living religious observance, not a civic date.

Mithuna covers the monsoon's arrival over most of India — mid-June to mid-July, the weeks when the rain reaches the interior. Raja Parba's ban on ploughing sits exactly there, before the first working of the wet ground. The sign runs about twenty-four days behind tropical Gemini because the two zodiacs are anchored differently: the Western signs start from the March equinox, which precesses westward roughly one degree every seventy-two years, while the sidereal signs stay fixed to the stars. The accumulated gap is now about 24°, measured for Indian purposes by the Lahiri ayanamsa adopted in 1955.

• Vedic Rashis
• World Zodiacs
• Gemini — the tropical counterpart.
• Religion
• Calendar