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

10
From the original concepts of the month and the year,
further concepts of the different kinds of month and the
year arose with the advance of astronomical knowledge.
We shall deal with these different kinds of the month and
the year in their respective contexts.
In these two verses, we have the definitions of Saura-
māna, Daiva-māna, chāndra-māna, Paitra-māna, Sāvana-
māna and Nākṣatra-māna, six of the nine mānas, ie mea-
sures of time.
Verses 21, 22, 23, 24, 25. The four yuga-pādas named
Kṛita, Tretā, Dwāpara and Kali consist of 4 × 432000,
3 × 432000, 2 × 432000 and 432000 mean solar years
respectively, the sum total of which consisting of
(4+3+2+1) × 43200 = 43,20000 mean solar years, is
calleda yuga. Each of the yuga-pādas above are inclusive
of what are called their respective Sandhyās and Sandh-
yāmsās which constitute one-twelfth of their own durations.
A Manu's duration consists of 71 yugas and 14 Manus
duration is reported to be the day-time of Brahma, whose
night is also of an equal duration.
The duration of a Manu, known as a Manvantara has
a Sandhyā-Kāla on either side, ie before and after, equal
to one Kṛita. If these are taken into account, the day-
time of Brahma amounts to one thousand yugas and it
goes by the name a Kalpa so that a complete day of
Brahma equals two Kalpas. The life-duration of Brahma
consists of one hundred years on this scale (where one
year = 360 days). This life-duration of Brahma goes by
the name Mahā-Kalpa, as reported by elders. In as much
as Time was without a beginning and will have no end
either, I do not know how many Brahmas have gone
before.
Comm. In these verses we are given what is known
as Brāhma-māna, the seventh of the nine mānas. Inciden-
tally we are also given the measures yuga-pādas, yugas,