The Surya Siddhanta

That which begins with a breath is called "measurable" time, while that which begins with an atom is known as "unmeasurable" time. *
Six breaths make one vināḍī approximately 24 seconds, and sixty of those are known as a nāḍikā approximately 24 minutes. || 11 ||

A "breath" (prāṇa) is the time taken for one inhalation and exhalation by a healthy person sitting at ease; it is also defined as the time required to pronounce ten long syllables. This breath is the starting point of "measurable" (mūrta) time. That which begins with a "trifle" (truṭi)—including units like the tatpara—is contained within a single breath and is designated as "unmeasurable" (amūrta) time original: "amūrta-sañjña". Now, because unmeasurable time is unsuitable for practical use and is secondary to the measurable time that constitutes it, the author sets aside the explanation of its divisions. Instead, focusing on measurable time as the primary subject for practical application, he describes the pala and the ghaṭī. By "six breaths," one pala also called a vināḍī is formed. Sixty of these palas are declared by those who know the truth of time to be one ghaṭikā. || 11 ||

Now, he describes the day and the month:

Sixty nāḍīs are proclaimed to be one sidereal day and night.
Thirty of those make a month; likewise, a civil month is measured by sunrises. || 12 ||

By sixty ghaṭīs, a sidereal relating to the stars day and night is declared. By the use of the word "but" (tu), it is implied that since the day and night are sidereal, the ghaṭīs composing them are also sidereal. This is because the circle of the stars the zodiac completes one revolution in these sixty ghaṭīs. A sidereal month consists of thirty such sidereal days. Since there are various systems of measurement, he defines the nature of the civil (sāvana) month. "Likewise," thirty days and nights—specifically those bounded by the rising of the sun, measured from one sunrise to the next—constitute a civil month.

• An alternative reading is "is said" original: "ucyate".

Prāṇa: The time of one breath, roughly 4 seconds.
Vināḍī/Pala: 6 breaths, roughly 24 seconds.
Nāḍikā/Ghaṭikā: 60 vināḍīs, roughly 24 minutes.
Nākṣatra: Sidereal, or measured by the stars.
Sāvana: Civil, or measured by sunrises.