A panchang (Sanskrit pañcāṅga, “five limbs”) is the almanac Hindu households, temples and astrologers consult to decide when to fast, when to celebrate and when to begin something. The name is literal: it describes every day by five quantities. Four of the five come straight from the positions of the Sun and the Moon, which is why a panchang has to be calculated for a place rather than printed once for a whole country.
1. Tithi — the lunar day
A tithi is the time the Moon takes to gain 12° on the Sun. The Moon gains a full 360° over a lunar month, so a month holds thirty tithis: fifteen in the bright half (Shukla paksha), from new moon to full, and fifteen in the dark half (Krishna paksha), from full back to new. The Moon’s speed varies through its orbit, so a tithi runs from roughly 19 to 26 hours and can begin at any hour of the day or night.
Because a tithi does not line up with the civil day, a panchang gives the tithi current at sunrise and the moment it ends. Most festivals are fixed to a tithi, which is why their Gregorian dates move from year to year — the subject of a separate article.
2. Vara — the weekday
The vara is the weekday, counted from sunrise to sunrise rather than midnight to midnight. Each is named for its ruling graha: Ravivara (Sun), Somavara (Moon), Mangalavara (Mars), Budhavara (Mercury), Guruvara (Jupiter), Shukravara (Venus) and Shanivara (Saturn). It is the one limb that is a count rather than a measurement of the sky.
3. Nakshatra — the Moon’s mansion
The sidereal zodiac is divided into 27 equal nakshatras of 13°20′ each, beginning with Ashwini at 0° Aries. The day’s nakshatra is the one the Moon occupies; at its average pace the Moon crosses one in about a day. The nakshatra the Moon held at birth is the starting point of Vimshottari dasha and of kundli matching — see the 27 nakshatras for the full list.
4. Yoga — the Sun and Moon together
Yoga here is a calendar term, not the discipline. It is found by adding the sidereal longitudes of the Sun and the Moon and dividing the sum into 27 parts of 13°20′. The 27 yogas run in a fixed order from Vishkambha to Vaidhriti. The muhurta texts count several as inauspicious for beginnings, Vyatipata and Vaidhriti most prominently.
5. Karana — half a tithi
A karana is half a tithi — the time the Moon takes to gain 6° on the Sun — so a lunar month holds sixty. Eleven names cover them. Four are fixed and occur once a month: Kimstughna in the first half of Shukla Pratipada, and Shakuni, Chatushpada and Naga at the very end of the dark half. The other seven — Bava, Balava, Kaulava, Taitila, Gara, Vanija and Vishti — repeat in that order eight times through the remaining 56 half-tithis.
Vishti, better known as Bhadra, is the karana most panchangs flag. Ceremonies are avoided while it runs, and it is the reason Holika Dahan and Raksha Bandhan sometimes fall a day later than the tithi alone suggests.
Why a panchang depends on where you are
A tithi, nakshatra, yoga or karana begins at the same instant everywhere on Earth. But the panchang reports what is current at sunrise, and sunrise is local — so two cities can print different tithis for the same date. This site computes sunrise for the place you choose and the Sun’s and Moon’s positions on the Lahiri ayanamsa, then reads all five limbs off those positions. Nothing is looked up in a printed table.
Tithi and karana depend only on the gap between the Moon and the Sun, so the choice of ayanamsa does not affect them. Nakshatra and yoga are measured on the sidereal zodiac and do depend on it.