Yoga in the panchang (not the same as yoga practice)
In the panchang, yoga is a combined period: the sum of the Sun's and Moon's sidereal longitudes, divided into 27 equal parts. It is not the same as the yogas of a birth chart.
What it is
There are 27 panchang yogas, from Vishkumbha to Vaidhriti. Each lasts about one day. Some are described as auspicious and some as inauspicious in the traditional texts.
How it is worked out or read
The yoga index is the integer part of the sum of sidereal Sun and Moon longitudes (mod 360), divided by 13 degrees 20 minutes, plus one.
Where it appears on this site
The panchang yoga and its end time are in the panchang tool. Chart yogas are a different topic; see yogas in the chart.
Adding up the two longitudes
To find the panchang yoga, add the sidereal longitudes of the Sun and the Moon, and reduce the sum to within 360 degrees. Divide by 13 degrees 20 minutes and take the whole part, then add one. The result is a number from one to twenty-seven, each naming a yoga. The sum grows at roughly the combined speed of the Sun and Moon, about 14 degrees a day, so each yoga lasts about a day. The calculation is simple once the two positions are known, and it is one of the reasons the panchang is considered a precise almanac.
What the names mean in practice
The yoga names, such as Vishkumbha, Priti, Ayushman and Siddhi, are traditional. Some are read as auspicious and some as inauspicious, and the classical lists assign each a quality. Many readers use them only as a quick guide when choosing a day for a minor activity. The more serious use is in muhurat rules, where yoga is one factor among several. A reader who wants to use yogas in muhurat should follow one text consistently and note which yoga list it uses.
Panchang yoga and the birth chart yoga
Readers often confuse the panchang yoga with the yogas of a birth chart. The panchang yoga is a timed period, computed from the Sun and Moon on a given day, and it changes every day. A chart yoga is a combination of grahas in a particular birth chart, and it is fixed for that person. The two words are the same, but the things they name are different. Keeping the distinction clear prevents a reader from treating a daily panchang yoga as a permanent feature of a person.
Yoga and the day's mood
Panchang yogas are often used by people to sense the mood of a day, choosing lighter tasks on a yoga read as difficult and more important work on one read as favourable. A reader can use this as a simple guide while remembering that the yoga is one of five limbs.
Yogas in the seasons of the year
Panchang yogas repeat through the year in a fixed sequence, so their pattern is the same each year even though the dates shift. A reader who notices this can see the yogas as a regular rhythm of the sky, rather than as a set of isolated days.