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THE CYCLE OF JUPITER.—THE SŪRYA SIDDHĀNTA WITHOUT THE BĪJA.
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139. Note that the interval of solar years between each Prabhava saṁvatsara is 60 when there is no suppression of a saṁvatsara in the cycle, 59 if there is one.

140. To find in what sign of the zodiac Jupiter stood at any time it is only necessary to calculate the ending-time of the saṁvatsara current at Mēsha saṁkrānti of the solar year. If the given day and time were earlier than that ending-time, that saṁvatsara—if later, the next following saṁvatsara—was current. The last column of Table XXXII. shows the sign in which Jupiter stood according to his mean longitude during the currency of the samvatsara so found.

Calculation by true longitude is dealt with separately.

Calculation by the Sūrya Siddhānta without the bīja.

141. For all purposes of chronology the Kaliyuga era begins at mean sunrise, taken as 6 a.m., on Friday, February 18th, 3102 B.C.; and that moment is the chronological "epoch" of the reckoning. The astronomical theory takes as the starting-point of the reckoning a general conjunction of the sun, the moon and the planets at the first point of the sign Mēsha, the initial point of the Hindu ecliptic; in other words an occasion on which the sun, the moon and the planets were considered as having been all on a line drawn from the earth to the First Point of Mēsha, so that the longitude of them all was then 0°. The Āryabhaṭīya, or First Ārya Siddhānta, places this conjunction at the chronological moment specified above, namely mean sunrise, or 6.0 a.m., on Friday, February 18th, 3102 B.C.; this may be called the "sunrise epoch" of the reckoning. The Present Sūrya Siddhānta places the conjunction at the preceding midnight; this may be called the "midnight epoch" of the reckoning;[1] and this latter work treats the mean Mēsha saṁkrānti as occurring at that midnight, and the sixty-year cycle of Jupiter as beginning with the saṁvatsara No. 27, Vijaya, commencing at that same moment. The elements of the Sūrya Siddhānta without the bīja are as follows:[2]—

A. Civil days in a mahāyuga of 4,320,000 solar years 1,577,917,828 days.
B. Revolutions of Jupiter in that period 1,577,364,220
C. One revolution, or A ÷ B 4332.3206523529 days.
D. One saṁvatsara, i.e., the planet's passage, by mean motion, through one sign, or 30° of arc; or C ÷ 12 0361.026721029 days.
(361 d. 0 h. 38 m. 29 s.)
E. Length of sidereal solar year 0365.2587564̇81̇ days.
(365 d. 6 h. 12 m. 37 s.)
F. Difference between lengths of solar year and saṁvatsara; or E − D 0004.232035452 days.
00(4 d. 5 h. 34 m. 8 s.)
G. śōdhya, or time-interval between true and mean Mēsha saṁkrānti (see above, § 39A, etc.) 2.170694̇ days.[3]
00(2 d. 4 h. 5 m. 48 s.)
H. Difference between solar year-length, E, and saṁvatsara-length in one whole cycle, or F × 60 0253.922127120 days.
I. E &minus H, or additive difference for beginnings of successive cycles 0111.336629361 days.
  1. ↑ The preceding passage has been remodelled from my original draft at Dr. Fleet's suggestion, whose article on the Kaliyuga era may be referred to. (Journal of the Royal Asiatic Society, 1911, pp. 479 ff.)
  2. ↑ I am indebted to Dr. Fleet for the following method of stating the elements, and for the values of A, B, C, D, in each case. I have verified the latter by comparison with the statements of other authorities.
  3. ↑ Mean Mēsha saṁkrānti is by so much later than true Mēsha saṁkrānti. (Ind. Cal., § 26, p. 11.)
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