Vedic timekeeping

The Hindu metrics of time can be summarized as below.

Hindu Kaala Vyavahara(Metrics of Time)

Table of contents 1 Sidereal metrics 1.1 Small units of time used in the vedas 2 Lunar metrics 3 Tropical metrics

Sidereal metrics

• a pranamu is the normal interval of blinking in humans, or approximately 4 seconds
• a vighadiya is 6 pranamus, or approximately 24 seconds
• a ghadiya is 60 vighadiyas, or approximately 24 minutes
• a muhurta[?] is equal to 2 ghadiyas, or approximately 48 minutes
• a nakshatra ahoratram or sidereal day is exactly equal to 30 muhurtas (Note: A day is considered to begin and end at sunrise, not midnight.)

Small units of time used in the vedas

• A leekshakamu is 1/60th of a pranamu, or 1/15th of a second;
• a lavamu is 1/60th of a leekshakamu, or 1/900th of a second;
• a renuvu is 1/60th of a lavamu, or 1/54,000th of a second;
• a truti is 1/60th of a renuvu, or the time it takes for a needle to penetrate a lotus leaf, or 1/3,240,000th of a second.

Lunar metrics

• a Tithi (also spelled thithi) or lunar day is defined as the time it takes for the longitudinal angle between the moon and the sun to increase by 12°. Tithis begin at varying times of day and vary in duration from approximately 19 to approximately 26 hours.
• a paksa or lunar fortnight[?] consists of 15 Tithis
• a masa[?] or lunar month (approximately 29.5 days) is divided into 2 paksas: the one between new moon and full moon is called gaura (bright); the oen between full moon and new moon krishna (dark)
• 2 lunar months are 1 Ruthu
• 3 Ruthus are 1 Aayanam
• 2 Aayanas are 1 year

Tropical metrics

• a jamu is 7½ Ghadiyas
• 8 jamus 1 half of the day(either day or night)
• an ahoratram is a tropical day[?] (Note: A day is considered to begin and end at sunrise, not midnight.)

Years are grouped into yugas (ages):

The Four Yugas

1,728,000 solar years[?]	Satya Yuga[?]
1,296,000 solar years	Treta Yuga[?]
864,000 solar years	Dwapar Yuga[?]
432,000 solar years	Kali Yuga

• One cycle of the the above four yugas is one mahayuga (4.32 million solar years[?])
• A manvantara consists of 71 mahayugas (306,720,000 solar years)
• After each manvantara follows one Sandhi Kala of the same duration as a Krita Yuga (1,728,000 solar years). (It is said that during a Sandhi Kala, the entire earth is submerged in water.)
• A kalpa consists of a period of 1,728,000 solar years called Adi Sandhi, followed by 14 manvantaras and Sandhi Kalas for a total of 1000 mahayugas or 4,320,000,000 (4.32 billion) solar years.
• Two kalpas constitue a day of Brahma; the life cycle of Brahma is one hundred years of Brahma, or 311 trillion years.