Yog (yoga) is the fourth anga (limb) of the panchang — tithi, vaar, nakshatra, yog and karana. At any moment you add the longitudes of the Sun and the Moon and split the result into 27 equal parts; the part you land in is that moment's yog. Because there are 27 of them, they are called nitya yogas (the daily yogas). Yog changes every day and is read alongside the other angas to judge a day's auspicious or inauspicious lean and its muhurat.