One almanac, five measurements
All five limbs are functions of the same two bodies — the Sun and the Moon — measured against the stars. They differ in what they divide:
| Limb | What it measures | How many | What it decides in a muhurat |
|---|---|---|---|
| Tithi | Moon's elongation from the Sun, in 12° steps | 30 per lunar month | The lunar day's fitness; rejects rikta tithis and Amavasya; anchors every festival |
| Vara | The weekday and its planetary lord | 7 | Refines by planet — Thursday's Jupiter blesses most rites; Tuesday's Mars is avoided for weddings |
| Nakshatra | The Moon's mansion on the ecliptic, 13°20′ each | 27 | Activity-suitability (Saptadha class) and the personal Tara Bala count |
| Yoga | Sun + Moon longitudes added, in 13°20′ steps | 27 | Veto power — Vyatipata and Vaidhriti sink an otherwise good day |
| Karana | Half a tithi — 6° of elongation | 11 (4 fixed, 7 repeating) | One rejection: Vishti (Bhadra) is avoided for all auspicious starts |
The convention that makes it all work: the day's limbs are read at the local sunrise. That is why a panchang is city-specific — and why Bela's daily panchang shows each limb with its exact end time, since the limb can change mid-day.
Tithi — the lunar day
A tithi ends when the Moon has pulled exactly 12° ahead of where it stood relative to the Sun at the last tithi's start. Thirty tithis make a lunar month: fifteen of the waxing (shukla) half from new moon to full, fifteen of the waning (krishna) half back. Because a tithi runs 22–26 clock hours, it does not respect the civil date — it can begin at noon, span two dates, or be "skipped" (kshaya) or "repeated" (vriddhi). This is the entire mechanics of festival dates: Diwali is the date on whose sunset the Amavasya tithi prevails; Janmashtami keys on midnight. Each festival's rule is noted on its festival page.
For elections the tithis are grouped in fives: Nanda (1, 6, 11), Bhadra (2, 7, 12), Jaya (3, 8, 13), Rikta (4, 9, 14) and Purna (5, 10, 15). The Rikta tithis and Amavasya are rejected for new beginnings in Muhurta Chintamani and the digests — the rule Bela applies before any finer screening.
Vara — the weekday
Each weekday belongs to a planet — Sunday to the Sun, Monday to the Moon, then Mars, Mercury, Jupiter, Venus and Saturn. The classical layer under it is the hora: each hour of the day is ruled in turn by the planets in their fixed order, starting from the day's own lord at sunrise. For muhurta, vara refines rather than decides: Jupiter's Thursday is praised for most auspicious rites, while Mars's Tuesday and Saturn's Saturday are avoided for weddings and housewarmings. The planetary weekdays also fix the dailyRahu Kaal andchoghadiya sequences.
Nakshatra — the Moon's mansion
The nakshatras divide the ecliptic into 27 mansions of 13°20′, each with a deity, a symbol and a temperament — the oldest layer of Indian astrology, already listed in the Vedic corpus. Two electional rules ride on them. First, the seven-fold Saptadhaclassification: fixed (sthira) mansions like Rohini and Uttara Ashadha for works meant to last; movable (chara) like Shravana for journeys; tender (mridu) like Anuradha for weddings; swift (kshipra) for quick works; mixed (mishra) for routine; and the fierce (ugra) and sharp (tikshna) mansions reserved for works of force. Second, the personal count — Tara Bala — which counts the day's mansion from your birth nakshatra and rejects the 3rd (vipat), 5th (pratyari) and 7th (naidhana) counts. The first rule is universal and appears in Bela's date lists; the second needs your chart and lives in the app. The full mansion-by-mansion table is in thenakshatra reference.
Yoga — the luni-solar sum
Add the Sun's and Moon's sidereal longitudes and divide the sum into 27 equal parts — those are the yogas, from Vishkambha to Vaidhriti. They measure the relationship of the two luminaries rather than either alone. Most yogas are neutral-to-good; Amrita, Siddhi, Brahma and Shubha are praised. Two carry an absolute classical veto:Vyatipata and Vaidhriti, under which no auspicious work is begun — Bela rejects dates under both, and you will see the rule named in every date's breakdown.
Karana — the half-tithi
Each tithi holds two karanas. Four are fixed to the month's ends (Shakuni, Chatushpada, Naga, Kimstughna); seven repeat through the month (Bava, Balava, Kaulava, Taitila, Gara, Vanija, Vishti). Ten of the eleven are usable; the exception is famous —Vishti, called Bhadra. The classics avoid beginning anything important in Bhadra, and one festival lives by the rule publicly: the Raksha Bandhan rakhi is tied only in Bhadra-free hours.
How the limbs combine
No limb alone decides. A day is elected when the nakshatra suits the act, the tithi is not rikta, the yoga is not Vyatipata or Vaidhriti, the karana is not Vishti, the weekday does not quarrel with the rite — and the moment itself sits clear ofRahu Kaal and its companions. That conjunction is what the score on everyBela muhurat date summarises, limb by limb, in the open.