Non commercial website, for knowledge sharing. Free to copy and use, if you find it useful. Kala or Time

Six and Sexagesimal system

A ghatika is further divided into 60 vinadikas.
Six prana or respiration is equal to one vinadi (23.93s).
Sixty vinadis equal one nadi or nazhi (also known as a ghatika =23m 56.06s).
one sidereal day = sixty nadis = 23h 56m 03.4446s
60 days = I rithu or season
1 year = 6 rithus or seasons
60 years cycle of Jupiter and Saturn to align

Ancient Indians had a six‐day week and 60 weeks per year.

Week

• The ancient Indians had a six‐day week.
• The ancient Egyptians had a ten‐day week.
• The ancient Babylonians who started the month on the day after the new moon, had the first, eighth, fifteenth and the twenty second day marked out for religious services. This was a kind of seven‐day week with sabbaths, but the last week might be of eight or nine days duration, according as the month, which was lunar, had a length of 29 or 30 days.
• The ancient Iranians had a separate name for each day of the month, but some days, at intervals of approximately seven, were marked out as Din‐i-Parvan, for religious practices. The pattern followed appears to have been similar to the Babylonian practice.
• The continuous seven‐day week was evolved on astrological grounds by unnamed Chaldean astronomers, long before the first century AD. Every one adopted it.

The seven day week was also introduced in India with the name of the day being the name of the planet which presides over the days based on the size of planets as seen from earth. This is similar to Greco-Roman system or ordering by ancient Babylonians.

Time division in current use:

Calendars

• The Kaliyuga calendar is apparently much older than the other surviving old calendars. The current Kali Yuga began after the Surya Siddhanta at midnight on a change of 17 at 18 February in the year 3102 BC in the proleptic Julian calendar.
• Tamil calendar System follows Solar year calendar system i.e., the time taken for one revolution of the Earth around the sun, or the mean time taken by the sun to return to the same position relative to the background of the fixed stars in the sky. Solar year is divided into 12 lunar months in accordance with the successive entrances of the sun into the signs of the zodiac, making the months to vary its length from 29 to 32 days.
• Telugu and kannada Calendar use 'Luni-Solar Calendar' and a year will have 12 or 13 months. One full Moon to the next full Moon is approxiimateluy 29.5 solar days which is equal to 30 tithi or lunar days. The tithi could begin at any time of a solar day so tithi that prevailed at sunrise is the tithi for the current day. The year consisted of twelve months, of 30 tithi each and was 360 tithi long. Three hundred sixty tithi is only 354 solar days and the solar year is 365.25 solar days thus every second or third year an extra month was added. It is interesting to note that a 360 tithi long year makes use of the very convenient number 360.
• Saaurya Maana or Solar Year : It consists of 12 months from Mesham to Meenam. Each month starts with Suns movement through the corresponding raasi starting with about April 13 or 14. It has about 365.24 days in a year.
• Saavan Maana : This year consists of 12 months of 30 days each and has 360 days.
• Nakshatra Manaana: Each month consists of movement of moon in the Nakshatras from Aswani to Revati. Twelve such months make a year with about 324 days.
• Baahraspatya Maana : Ths is based on movement of Guru or Jupiter in different signs and is about 361 days duration. This has to do with kumbha mela functions of different rivers .

Magic Numbers

1. 60 has factors 2, 3, 4, 5, 6. It was used to divide a day in to nazhi and vinadis. Year is divided in to 6 seasons of 60days approx. 60 year cycles is used to name years.
2. 108 has factors 2, 3, 4, 6, 9. No 108 is a Harshad number, which is an integer divisible by the sum of its digits
3. 432 has factors 2, 3, 4, 6, 8, 9. Like 108, 432 is also a Harshad number. 432 was considered as magic number for astronomical calculations. 2160 and 4320 is exactly divisible by 2, 3, 4, 5, 6, 8, 9, 10, and 12. (except 7 and 11). Also exactly divisible 18, 20, 30, 60 and 360 used in astronomical calculations.
   4320/7 = 617.142857142857 = 614+PI
   4320/11 = 392.727272 repets of 72
   
4. Kalacakra calendar in use, 60 year cycle starting with Prabhava, is by Pandita Somanatha of Kashmir/Himalayas, in 367 CE. The earth's axis wobble that causes the precession of the equinoxes is approximately 25,920 years or 432 sixty year cycles.

Cyclic Nature of Time - Yugas

1. Basic cycles is day for earth rotation, month for moon orbital time, and year for earth orbital time. One year divided in to 6 rithus or seasons
2. Brhaspati Yugas: 12 years - Surya, Chandra, Brhaspati are aligned in Kumbha rashi. There is also 60 years variant.
3. SaptaRishi Yuga : The Ursa Major, seven stars known as the Big Dipper (or the Plough or seven sages) traces a circuit in the sky around the North Pole of the earth. Ursa Major passes through each of these nakshatras in 100 years, and completes a single rotation in approx 2,700 years.
4. Romaka Siddhantam : 2850 luni solar years
5. The precession of the equinoxes was taken as 25,920 years (27,000 in some scriptures). This was also considered as one mahayuga. March equinox takes 2160 years to move feom one rasi to next. 4320 years for one rithu or 2 rasis (6 rithus make one maha yuga)
   
6. The earth wobbles in space so that its tilt changes between about 22 and 25 degrees on a cycle of about 41,000 years.
7. The earth's orbit around the sun is not circular, but elliptic. The closest approach of the earth to the sun is called perihelion, and it now occurs in January. This change in timing of perihelion and occurs on a period of 22,000 years. 11,000 years ago, perihelion occurred in July, making the seasons more severe than today. The "roundness", or eccentricity, of the earth's orbit varies on cycles of 100,000 and 400,000 years, and this affects how important the timing of perihelion is to the strength of the seasons. The combination of the 41,000 year tilt cycle and the 22,000 year precession cycles, plus the smaller eccentricity signal, affect the relative severity.

Planetary Alignment and Mahayugas

Exact Planetary Alignment may never happen. It may just be a myth.

The alignment of planets has generated superstitious beliefs throughout history. Every century, planets take up positions in the night sky creating the impression of being in more or less a straight line. History shows that planetary alignments are harmless. On 5 Feb 1962 during a solar eclipse, an extremely rare grand conjunction of the classical planets occurred, after 1821. All 5 of the naked-eye planets plus the Sun and Moon, all of them within 16° of one another on the ecliptic. Saturn, Jupiter, Mars and Venus were on one side of the Sun, while Mercury and Earth were on the opposite side. All grahas aligned in capricorn rashi. When the Moon crossed between the Earth and the Sun, the eclipse was visible over India.

One calculation of two dimensional alignments within around thirty degrees (about as close as they can get) shows that the last such alignment was in 561 BC, and the next will be in 2854. However, they do make formations in our visible sky every year.

Precession year or the time taken for one cycle of precession to complete= 25920 years. 60 degrees (1/6th or 1 season) of this precession circle is covered in 4320 years. 432 is a magic number by astronomers.

Ancient astronomers tried to predict alignment of grahas using lowest common multiple of time of revolution of all grahas. Few are listed below:

• In Daca Ghittika and Kaala Kriya, Arya Bhatta wrote, "Grahas start from one straight line, and all will reach the same straight line in one yugam or 432,000 Years.
  Multiplied by 10 is 1 Mahayugam (4,320,000 years), which may be better alignment.
• Poorva Surya Siddhantham uses 180,000 years for graha alignment.
• Surya Siddhantam mentions 4,200,000 years.
• Naveena Siddhanthams : 4,320,000 years (4:3:2:1 Ratio for Kruta, Treta, Dwapara and Kali).
• Berossus, the priest of Marduk of Babylonians noted in the 3rd century BC that 432,000 solar years was the time that had elapsed from the origin of divine kingship to the end of the world, the planets would conjunct in Capricorn.
• The adoption of a cycle of 4,320,000 (or its multiples) avoids inconvenient fractions. Number 4,320,000 is divisible by several of the small numbers (like 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 16, 18, 20, 24, 25, 27, 30, 60) occurring frequently in astronomy, So it would have been chosen.

Some figures based on some facts, used in stories like Bhagavadam:

Around 500 BC to 500AD, some would have visited polar region, where one day is one year. 
This was extrapolated few more levels.
Poets use magic numbers 27/28, 432 (108*4 or 36*12) and 360 for astronomical approximation.
Yuga starts when planets align exactly in a straight line, which may never happen. 
Easy to add zeros behind any number, to make it an interesting story.

1 pithru (ancestor) Day = 1 lunar month
1 Deity Day (day and night) = 1 year
1 Deity Year = 360 earthly years 
1 Chatur yuga = 4,320,000 years
1 Manvantara = 71 Chaturyugas = 306,720,000 years
A Brahma's day or Kalpa = 1,000 (994?) Chatur yugas = 4.32 billion years = 14 Manvantara
1 Brahma Day (day and night)  = 2 Kalpa

Brahma year = 2.11 trillion years. Brahma has completed 50 years and is in 51st year. After 100 Brahma years, new brahma is born and cycle continues. The current Kalpa is known as the Shveta-Varaha Kalpa. Within this Kalpa, six Manvantaras have already passed and we are living during the seventh Manvantara, and our Manu is Vaivasvata Manu. Indra is Purandar. Saptarishis are Kashyapa, Atri, Vasistha, Vishwamitra, Gautama, Jamadagni and Bharadvaja. Within this Manvantara, we are currently in the Kali Yuga of the 28th Chaturyuga.
The current measurement of the age of the universe is estimated to be 13.8 billion years

Personal View of Author:

All cultures have Golden, Silver, Copper and Iron age. Old is always GOLD and things are becoming bad and world will end. So many end of world predictions have gone wrong. During socrates, some one wrote, world will soon end because of evil, BUT WE ARE STILL LIVING.

Tradition is a form of collective memory, sometimes documented. Norms do change. Every yuga has its own religious, spiritual practices that may be followed in one epoch but do not apply to another.

Puranas and stories ( or Indian history) have generally 4 yugas or leval of social order.
(1) Continuous conflict between 2 parties, say devas and asuras. There are many animal-human beings and so on. Females and children are treated as assets/possessions. Importance for strength to win conflicts.
(2) Polygamy, kidnapping of wives, fire purification/testing, special treatment of favourite wives/children etc are norms. Loyalty, dicipline, sacrifice, complex yagams are given importance.
(3) Polygamy/Polyandry, fight between kins for royal positions, sati, rules/order for expanding empire, rules for gambling are norms. Even wife, siblings and children can be gambled. Slavery is accepted. Importance for order, justice and truth.
(4) In history books, we come across: Polygamy, Sati, Slavery etc.
Current age is more indivualism, freedom to pursue any profession, globalization etc. Each age or time is different. ALL ARE GOLDEN AGES.

Additional Notes: Bhagavatam

Brahma represents our universe which has birth and death, a big bang and a big cruch, from a navel singularity. Vishnu represents the eternity that lies beyond our universe which has no birth or death and that which is eternal! Brahma is the personification of our temporary physical universe, described as a lotus blooming out of the navel.

The universe is often said to be born from the sacred syllable Om, or from an inert void. From this void desire was born, and from desire came humans, gods and demons.

The universe was created out of the parts of the body of a single cosmic man Purusha when his body was sacrificed.

The universe was created by Hiranyagarbha (here interpreted as 'the golden embryo') or by Prajapati who was born from the Hiranyagarbha (here interpreted as 'the golden womb'). A universe exists for about 4.32 billion years (one day of Brahma). Destroyed by fire or water elements, named Pralaya. Then repeats for 100 Brahma years with a break.

Bhagavatam states that matter exists in two conditions: manifest; and unmanifest. When matter is transformed to a manifest condition, the universe is created and when the universe is annihilated, matter is transformed back into its unmanifest condition. For order, a conscious being is required. Matter's tendency is to increase disorder.

Bhagavatam tells of innumerable universes. Each one is contained in a spherical shell surrounded by layers matter, space and spirit. The region within the shell is called the Brahmanda, or “Brahma egg.” Talks about disk or plane—called Bhu-mandala with an upper, heavenly half and a subterranean half. Bhu-mandala is divided into a series of geographic features, traditionally called dvipas, or “islands,” varshas, or “regions,” and oceans. In the center of one dvipa, Jambudvipa stands Sumeru Mountain or the world axis. *Number 7, used to classify geography, planets etc.