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

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during that month. The next lunar month is termed as
the Nija-māsa or the month which is the true. In this
convention however, there may occur two Saṁkrāntis in
one particular lunar month. For this to happen two cri-
teria are to be satisfied namely that, that particular lunar
month must be greater than the concurrent solar month
and secondly one of the two Saṁkrāntis must occur imme-
diately after a New-moon so as to permit the second Saṁk-
rānti to occur just before the lapse of the lunar month.
The Sun coming to his perigee roughly about the lunar
month Mārgasira, and as such having the quickest motion
at that point, he covers the length of the Rasi of 30° within
the shortest span of time making that Solar month shorter
than the corresponding lunar month. Since the months
Kārtica and pausha, one before and the other after Mārga-
sira, also being thus longer than the corresponding solar
months, two Sankrāntis could occur, if at all, in these three
lunar months. If they occur, that lunar month is termed
a Kshayamāsa. Since two lunar months are to correspond
to two Saṁkrāntis, convention has it that two lunar months
lapse simultaneously during that lunation, the previous
lunation running during the forenoon and the subsequent
lunation during the afternoon. Thus a Kshaya māsa is also
called a yugalībhūta māsa or a twin māsa, which therefore
makes one lunation virtually vanish. On account of this
vanishing’, it is called a Kshayamāsa. After what an inter-
val of time this Kshaya māsa occurs how a month precedes
it having no Saṁkrānti and how again a lunation follows
it without a Saṁkrānti will be seen in a subsequent
context. This convention pertaining to the institution
of an Adhikamāsa goes by the name ‘Inter-calation’.
It was mentioned before that on an average an
Adhikamāsa occurs once in 32½ solar months roughly–Also,
Adhikamāsas are the excess of lunations over the solar
months in a given period. There being 51840000000 solar
months in a Kalpa and 53433300000 lunations the number
of Adhikamāsas is therefore 1593300000 as mentioned,