Vedang Jyotish

The Yuga Cycle

The Vedang Jyotish (वेदाङ्ग ज्योतिष), attributed to Rishi Lagadha (~1400 BCE), defines a 5-year Yuga as the fundamental calendrical unit. Within one Yuga:

• 1830 savana (civil) days
• 60 saura (solar) months
• 62 chandra (synodic lunar) months — including 2 adhik (intercalary) months
• 67 nakshatra (sidereal lunar) months
• 1860 tithis (lunar days)
• 1835 nakshatra days (sidereal days)

The year begins at the winter solstice (Uttarayana) with the Sun and Moon conjoining near Dhanishtha nakshatra — a reference point that helps date the text. Each lunar month is divided into two parvas (fortnights) — the term used in Vedang Jyotish for what is later called paksha: Shukla (waxing/bright half) and Krishna (waning/dark half).

Intercalary Months (Adhik Maas)

12 lunar months (≈354 days) fall short of the solar year (366 days in VJ) by about 11 days. Over 5 years this deficit accumulates to ~55 days — nearly two full lunar months. Two adhik (intercalary) months are inserted at fixed positions in the Yuga to re-align the luni-solar calendar:

• 1st Adhik Maas — Adhik Ashadha, inserted near the summer solstice of Year 3 (Idavatsara). By the middle of the Yuga the lunar calendar has drifted ~1 month ahead; this intercalation corrects it.
• 2nd Adhik Maas — Adhik Pausha, appended as the last month of Year 5 (Idvatsara). The remaining drift is absorbed here so that the next Yuga begins cleanly at the winter solstice with Sun and Moon again at Dhanishtha.

These positions are fixed by rule, not observation — a hallmark of the Vedang Jyotish's purely arithmetic (yuga-based) approach to timekeeping, distinct from the later observational Siddhantic system.

Solar Months & Ritus

The pairing of solar months with the six seasons is attested in the Krishna Yajurveda:

मधुश्च माधवश्च वासन्तिकावृतू ।
शुक्रश्च शुचिश्च ग्रैष्मावृतू ।
नभश्च नभस्यश्च वार्षिकावृतू ।
इषश्चोर्जश्च शारदावृतू ।
सहश्च सहस्यश्च हैमन्तावृतू ।
तपश्च तपस्यश्च शैशिरावृतू ॥

— Taittiriya Samhita, Kanda 4, Prapathaka 4, Anuvaka 11 (Krishna Yajurveda)

Madhu & Madhava are the months of Vasanta (spring), Shukra & Shuchi of Grishma (summer), Nabhas & Nabhasya of Varsha (monsoon), Isha & Urja of Sharad (autumn), Sahas & Sahasya of Hemanta (early winter), and Tapas & Tapasya of Shishira (late winter).

Parva Nakshatras — The Mnemonic Verse

Vedang Jyotish encodes the starting nakshatra of each parva (fortnight) across the entire Yuga in a compact mnemonic. Each syllable is a shorthand for a nakshatra:

जौ द्रागः खे श्वे ऽही रो षा चिन्‌ मू षण्यः सू मा धा णः ।
रे मृ घाः स्वा ऽऽपो ऽजः कृ ष्यो ह ज्ये ष्ठा इत्युक्षा लिङ्गैः ॥

— Vedang Jyotish (Rik recension)

Each syllable in this verse is the first syllable (or a recognizable abbreviation) of one of the 27 nakshatras. Reading them in sequence gives the starting nakshatra for each successive parva across the 124 parvas (62 months × 2) of the Yuga. This allowed priests to determine which nakshatra the Moon would be near at the start of any given fortnight — entirely by memorizing a single verse, without observation or calculation.