Bharatiya Jyotihshastra (History of Indian Astronomy), translated by R. V. Vaidya v2.c15.3

v2.c15.3

(1) Europeans first obtained some knowledge worth the name about Indian Astronomy from a copy of an astronomical work procured from Siam. This work has adopted 365d-15i-31p-30v as the length of the year (which is the same as that in the original Sūrya siddhānta and Khaṇḍakhādyaka). Cassini, a French astronomer, says that the epochal positions have been given for Saturday, the new moon day, 21st March, 638 A. D. (According to the original Sūrya Siddhānta, the mean Aries ingress occurred on the 2nd lunar day of the bright half of Vaiśākha, Śaka 560, i.e. Sunday the 22nd March 638, at 12gh. 58p. after (mean) sunrise, and the preceding mean new moon of Caitra occurred on Friday at 49gh-35p i.e. on Saturday, 21st March according to European reckoning) The original epochal positions may have been true for Narasingpur near Pithāpur in Godāvari district or for Vārāṇasi. The sun's apogee given in this work is 80°. The maximum value of the equation of centr of the Sun is 2°-14' and that for the Moon is 4°-56'. This shows that the work may have followed either the original Sūrya Siddhānta or some Karaṇa work now lost, by Āryabhaṭa I who followed the Sūryu Siddhānta.