ASTRONOMY IN VEDANGA JYOTHISHYA
Yuga definition states that Yuga always starts when Sun-moon are in conjunction near Shravishta. In YVJ 29, ‘sapanchakah’ is used while describing the Yuga. Author would like to interpret this as five day Yuga beat cycle error. This is demonstrated below while tracking six consecutive Yuga conjunction of sun/moon near Shravishta.
Starting from Jan 02, 1372 BC Gregorian we track six Yuga’s. On that day Sun/Moon are at conjunction one day after winter solstice. Next Yuga end occurs on Jan 05, 1367, which is 1830 days from previous Yuga, with conjunction occurring 6 days after winter solstice. Slippage of 5 days in solstice is evident.
At end of next Yuga, sun-moon conjunction occurs on Jan 11, 1362. This Yuga again has 1831 days, and conjunction occurs 15 days after winter solstice It has a further 5-day slippage per Yuga.
The next Yuga can start either on Dec 18 1858 BC (1803 days) 14 days before winter solstice. Alternately Jan 16.1837 (1831 days) is the next conjunction of sun/moon, nearly 14 days after winter solstice. The Priest would have to make a judgment about when the next Yuga between these two days one lunar month apart.
Next Yuga starts on Dec 21, 1353 BC, which again is either 1828 days or 1858 days based on deciding which of the previous two Yuga beginnings, were accepted.
From this Yuga onwards the Solstice and beginning of Yuga start getting near each other
Dec 21 1358 BC is only 12 days before Solstice and the next Yuga on Dec 27 is only 4 days before Solstice. The day count is near 1830
Clearly the Yuga beginning has a beat cycle of maximum of plus or minus 15 days,(a 5-day error per Yuga) with winter solstice and the days count between Yuga has to slip to about 1803 days. The use of expression ‘sapanchakah’ in YVJ 29 can be interpreted as Lagadha’s awareness of solstice and sun/moon conjunction having this type of beat cycle error. The fact that once in five to six Yugas the number f days per year has to be adjusted one lunar month away is not explicitly states in the available texts of Vedanga Jyotishya.