सिद्धान्तशिरोमणि: गणिताध्याय (भास्कराचार्य - ग्रहगणित, मध्यमाधिकार व स्पष्टाधिकार सटीक)

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resulted in a difference between the computed planetary
positions and their observed positions. So, the originator
of this Bīja-Saṁskāra, noting the differences in his own
time devised a formula, which could account for those
differences. But this formulation was bound to go wrong in
later times as long as the daily motions are not corrected
to the minutest extent possible and as long as the funda-
mental basis of the conjunction of all the planets and pla-
netary points is not proved. This seems to be the reason
why so may texts were written incorporating small diffe-
rences in different times as reported by Gaṇēśa (1507 A.D.)
in his work Bṛihat-Tithi-Chintāmaṇi in the words "The
calculations of planetary positions according to the
methods indicated by Brahma, Vasishtha and Kasyapa
Siddhantas held good in their own times, but grew obsolete
later; Then Maya, the demon at the end of Krita obtained
the science from the Sun God, which again grew obsolete
in this Kaliyuga wherein parāśara began to hold the ground
for a good length of time. Then Āryabhata rectified the
methods; when even those methods grew obsolete, Durga-
Simha, Varāha Mihira and others set them right. Again
Brahmagupta came into the picture to rectify the methods
by his own observations. Then Came Kēśava (Gaṇēsa's
father) who rectified further. After a lapse of sixty years,
his son Gaṇesa has now to correct the Science. If this
also grows obsolete (as it is bound to) in course of time, let
others again rectify it by observing conjunctions of the
Moon and planets with the asterisms."
Obsoleteness arises out of two contexts, one a justifi-
able situation and the other based upon a wrong premise.
The first is as follows. Suppose as a first approximation
we take the length of an year as 365 days. We will have
committed an error nearly ¼ of a day, so that the error
accures to a day in 4 years. Thus the convention of the
leap year arose so that during four years we give a day
more to February. Here again we have overestimated the
error by nearly 1/100th of a day. Hence in 400 years the