The fourth limb of the day
The Panchang describes each day through five limbs: Tithi, Vara, Nakshatra, Yoga and Karana. The fourth of these, Yoga, is a measure of the combined movement of the Sun and the Moon. It is different from the Yogas in a birth chart, which are planetary combinations, described on the page about Yogas in Vedic astrology. Here the word means a division of time in the daily almanac.
There are 27 Yogas. Each lasts roughly a day, and each has a name and a character that traditional almanacs use to judge the quality of a period. For an overview of all five limbs, see What is Panchang?.
How a Yoga is calculated
The calculation is simple. Take the sidereal longitude of the Sun and the sidereal longitude of the Moon and add them. If the sum is more than 360 degrees, subtract 360. Then divide the circle into 27 equal parts of 13 degrees 20 minutes each. The part in which the sum falls is the Yoga.
When the sum is between 0 and 13 degrees 20 minutes, it is the first Yoga, Vishkambha. When it is between 13 degrees 20 minutes and 26 degrees 40 minutes, it is the second, Priti. The pattern continues until the sum reaches the full circle, at which point the cycle begins again.
The Sun and Moon move together at a combined speed of about 14 degrees a day, so a Yoga lasts about a day. Its real length varies from roughly 20 to 26 hours because the speed of both bodies changes through the year. As with the Tithi, the Yoga that is active at local sunrise names the day.
Because it uses sidereal positions, the Yoga depends on the ayanamsha. See Lahiri ayanamsha. This is a difference from the Tithi and the Karana, which depend only on the angle between the Sun and Moon.
The 27 Yogas
The names, in order, are:
- Vishkambha
- Priti
- Ayushman
- Saubhagya
- Shobhana
- Atiganda
- Sukarma
- Dhriti
- Shula
- Ganda
- Vriddhi
- Dhruva
- Vyaghata
- Harshana
- Vajra
- Siddhi
- Vyatipata
- Variyana
- Parigha
- Shiva
- Siddha
- Sadhya
- Shubha
- Shukla
- Brahma
- Indra
- Vaidhriti
Qualities of the Yogas
Traditional texts sort the Yogas by their quality. Names such as Priti, Ayushman, Saubhagya, Shobhana, Sukarma, Dhriti, Vriddhi, Dhruva, Harshana, Siddhi, Variyana, Shiva, Siddha, Sadhya, Shubha, Shukla, Brahma and Indra are considered favorable. Their meanings are close to their English translations, such as love, long life, good fortune, beauty, good deed, steadiness, growth and success.
Nine Yogas are traditionally seen as difficult: Vishkambha, Atiganda, Shula, Ganda, Vyaghata, Vajra, Vyatipata, Parigha and Vaidhriti. Their names suggest obstacles, such as a pillar, a great danger, a spear, a knot or a thunderbolt. Of these, Vyatipata and Vaidhriti are the most cautious, because they are linked with a great calamity, and many families avoid starting new work during them.
How Yoga is used
Almanacs list the Yoga of each day with its start and end times. Traditional practice uses it in three main ways.
Choosing a muhurta. When setting a date for a ceremony, a purchase or a journey, astrologers check that the Yoga is favorable. A good Tithi and Nakshatra with a difficult Yoga may lead to a different choice.
Noting the quality of the day. Some people read the Yoga as the tone of the day, in the same way as the Moon phase.
Naming a person. In some traditions, the Yoga of the birth day is read as an extra detail of temperament, though this is minor.
For people outside the tradition, the Yoga is the least known of the five limbs. It is useful for completeness, and for anyone who wants to follow a printed Panchang.
Yoga and the other limbs
The five limbs describe one moment from five angles. The Tithi is the lunar day, the Vara is the weekday, the Nakshatra is the position of the Moon among the stars, the Yoga is the combined position of Sun and Moon, and the Karana is half a Tithi. A good muhurta is one where several limbs agree.
A word of balance
Scientific studies have not shown that these time qualities change the outcome of an event. The Yoga is part of a traditional calendar and many people use it for culture and routine, not for practical effect. If a difficult Yoga falls on a day you must act, there is no reason to delay an important decision because of it.