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

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In the case of obtaining the Suddhi, if an Adhikamāsa,
which did not actually occur, is obtained by calculation,
then the Suddhi is to be increased by 30, so that the
Ahargaṇa is not affected by the un-occuring Adhikamāsa.
Comm. The computation of the Adhikamāsas or inter-
calary months proceeds under the consideration of mean
lengths. So, it is likely that an Adhikamāsa may occur
un-warranted by calculation or may not occur in spite of
its being shown by calculation. Further, an Adhikamāsa
may be delayed in occurence by the fact that though the
luni-Solar reckoning has gained over the solar by one
mean lunation, the lunation at that point may still con-
tain a Samkrānti, the preceding particular lunar month
being smaller in length than the mean. Thus the conven-
tion made with respect to the occurence of an adhikamāsa,
namely that the lunation which does not carry a Samkrānti
is to be construed as an adhikamāsa, may also delay the
occurence of the Adhikamāsa, though shown in calculation.
Similarly an Adhikamāsa may be preponed though not
warranted by computation by the same logic.
Verse 6. The criteria of an Adhikamāsa and a
Kshayamāsa.
A lunation which does not carry a Samkrānti is an
Adhikamāsa; whereas a lunation which carries two Sam-
krāntis is to be taken as a Kshayamāsa. The Kshaya-
māsa, occurs only in the course of the three lunar
months named Kārtica, Mārgasīrsha and pausha and
not during any other lunar month; when a Kshayamāsa
occurs, then during the course of that year there will be
two Adhikamāsās occuring on either side of the Kshaya-
māsa.
Comm. The institution of intercalation has been
explained to some extent under verse 10 of the Bhagaṇādh-
yāya. We shall see some more particulars of intercalation.
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