Yugas, according to the book Pillar of Celestial Fire by Robert Cox
Yuga ²⁵⁄₂₇ Sandhi ²⁄₂₇ ∑ (sum) ²⁷⁄₂₇
∑ (sum) ¹⁰⁄₁₀ 12 000 years 960 years 12 960 years
Krita ⁴⁄₁₀ 4 800 years 384 years 5 184 years
Treta ³⁄₁₀ 3 600 years 288 years 3 888 years
Dwapara ²⁄₁₀ 2 400 years 192 years 2 592 years
Kali ¹⁄₁₀ 1 200 years 96 years 1 296 years

In his book Pillar of Celestial Fire (pages 158–168), Robert Cox outlines how each half-period of the precessional cycle may be divided into four yugas or ages. It says that they span a total of 12,000 years, and their periods display the relative ratios of 4:3:2:1. At the junction between ages there are shorter periods of transition, called sandhis. Their relative ratios correspond to those of the ages themselves.


On page 160 of The Pillar of Celestial Fire it says:


The four Ages described above pertain to the evolution of human civilization on Earth. There are much longer cycles that pertain to the evolution of the Galaxy as a whole. In accordance with the principle “as above, so below,” these longer cycles have the same names: Krita, Treta, Dwapara, and Kali, and display the same relative ratios of 4:3:2:1. However, each “year” in the larger cycle is a “celestial year” that is composed of 360 human years. The four celestial Yugas (not including their sandhi periods) thus span a total of 12,000 x 360 = 4,320,000 years.


Employing the information in the quote above, I've deviced the table below to demonstrate the resulting relationships between yugas and sandhis on a celestial scale, and their total span, from this perspective—given that the sandhi periods on a celestial scale have the same relation to their respective yugas as do their counterparts on a terrestrial scale.






Celestial Yugas, derived of info. in Pillar of Celestial Fire by Robert Cox
Yuga ²⁵⁄₂₇ Sandhi ²⁄₂₇ ∑ (sum) ²⁷⁄₂₇
∑ (sum) ¹⁰⁄₁₀ 4 320 000 years 345 600 years 4 665 600 years
Krita ⁴⁄₁₀ 1 728 000 years 138 240 years 1 866 000 years
Treta ³⁄₁₀ 1 296 000 years 103 680 years 1 399 680 years
Dwapara ²⁄₁₀ 864 000 years 69 120 years 933 120 years
Kali ¹⁄₁₀ 432 000 years 34 560 years 466 560 years


In the book Hebrew Astrology the author Sepharial has presented another scale for the terrestrial yugas. It says on page 61:


A division of the Great Year by 6 yields the significant period of 4320 years which is the basis of a series which together constitute the Mahayuga or Great Age of the Hindu system, and which has undoubtedly arisen from the same source. Thus: 
Kali yuga   4,320  or    120 solar periods of 36, or 6 x 6
Dvapara yuga   8,640    240
Treta yuga 12,960    360
Satya yuga 17,280    480
Mahayuga 43,200 1,200 solar periods
The prophetic cycle of 2,520 years is 70 solar periods of 36 each.


Based on this I've made the tables to the right and below.











Yugas based on Hebrew Astrology by Sepharial, ²⁷⁄₂₇ version 3
Yuga ²⁵⁄₂₇ Sandhi ²⁄₂₇ ∑ (sum) ²⁷⁄₂₇
∑ (sum) ¹⁰⁄₁₀ 40 000 years 3 200 years 43 200 years
Krita ⁴⁄₁₀ 16 000 years 1 280 years 17 280 years
Treta ³⁄₁₀ 12 000 years 960 years 12 960 years
Dwapara ²⁄₁₀ 8 000 years 640 years 8 640 years
Kali ¹⁄₁₀ 4 000 years 320 years 4 320 years

Yugas based on Hebrew Astrology by Sepharial, ²⁷⁄₂₇ version 4
Yuga ²⁵⁄₂₇ Sandhi ²⁄₂₇ ∑ (sum) ²⁷⁄₂₇
∑ (sum) ¹⁰⁄₁₀ 43 200 years 3 456.0 years 46 656.0 years
Krita ⁴⁄₁₀ 17 280 years 1 382.4 years 18 662.4 years
Treta ³⁄₁₀ 12 960 years 1 036.8 years 13 996.8 years
Dwapara ²⁄₁₀ 8 640 years 691.2 years 9 331.2 years
Kali ¹⁄₁₀ 4 320 years 345.6 years 4 665.6 years

…

Terrestrial Yugas, according to Ravel Śāśwata Petershagen
Sandhyā ¹⁄₁₂ Yuga ¹⁰⁄₁₂ Sandhyānśa ¹⁄₁₂ ∑ (sum) ¹²⁄₁₂
∑ (sum) ¹⁰⁄₁₀ 1 080 years 10 800 years 1 080 years 12 960 years
Kṛta|Satya ⁴⁄₁₀ 432 years 4 320 years 432 years 5 184 years
Tretā ³⁄₁₀ 324 years 3 240 years 324 years 3 888 years
Dvāpara ²⁄₁₀ 216 years 2 160 years 216 years 2 592 years
Kali ¹⁄₁₀ 108 years 1 080 years 108 years 1 296 years

In the table above I show my new method of dividing the yugas. Instead of a single sandhi period between each yuga, I have included two junctional periods or twilight periods relative to each yuga; one before called sandhyā, and one after called sandhyānśa.
Traditionally though, it is the yugas of a larger scale which are most frequently mentioned. The total timespan of a ćaturyuga, comprising four yugas—on the larger scale—is described as concisting of 4 320 000 Earthly years. But rarely is it conveyed whether or not this number includes the junctional periods of sandhyā and sandhyānśa between the yugas. Taken that they should be included, I have made an alternative table below where I've multiplied each number in the top table with 333.333333∞ to arrive at the total span of 4 320 000 years.


Celestial Yugas version 1, according to Ravel Śāśwata Petershagen
Sandhyā ¹⁄₁₂ Yuga ¹⁰⁄₁₂ Sandhyānśa ¹⁄₁₂ ∑ (sum) ¹²⁄₁₂
∑ (sum) ¹⁰⁄₁₀ 360 000 years 3 600 000 years 360 000 years 4 320 000 years
Kṛta|Satya ⁴⁄₁₀ 144 000 years 1 440 000 years 144 000 years 1 728 000 years
Tretā ³⁄₁₀ 108 000 years 1 080 000 years 108 000 years 1 296 000 years
Dvāpara ²⁄₁₀ 72 000 years 720 000 years 72 000 years 864 000 years
Kali ¹⁄₁₀ 36 000 years 360 000 years 36 000 years 432 000 years

But, tradition has it that 1 year of the gods—or devas and devīs—is equal to 30 × 12, or 360 Earthly years. By multiplying the numbers in the topmost table with 360, I get the table below showing another alternative for a timespan of the four Celestial yugas (version 2), which is the solution when the junctional periods are not included in the total timespan of a ćaturyuga of 4 320 000 years but are instead added to that number.


Celestial Yugas version 2, according to Ravel Śāśwata Petershagen
Sandhyā ¹⁄₁₂ Yuga ¹⁰⁄₁₂ Sandhyānśa ¹⁄₁₂ ∑ (sum) ¹²⁄₁₂
∑ (sum) ¹⁰⁄₁₀ 3 88 800 years 3 888 000 years 3 88 800 years 4 665 600 years
Kṛta|Satya ⁴⁄₁₀ 155 520 years 1 555 200 years 155 520 years 1 866 240 years
Tretā ³⁄₁₀ 116 640 years 1 166 400 years 116 640 years 1 399 680 years
Dvāpara ²⁄₁₀ 77 760 years 777 600 years 77 760 years 933 120 years
Kali ¹⁄₁₀ 38 880 years 388 800 years 38 880 years 466 560 years


These six tables below and to the right are based on the quote in the left column, from the book Hebrew Astrology by Sepharial.


Yugas based on Hebrew Astrology by Sepharial, ¹²⁄₁₂ version 1
Sandhyā ¹⁄₁₂ Yuga ¹⁰⁄₁₂ Sandhyānśa ¹⁄₁₂ ∑ (sum) ¹²⁄₁₂
∑ (sum) ¹⁰⁄₁₀ 3 600 years 36 000 years 3 600 years 43 200 years
Kṛta|Satya ⁴⁄₁₀ 1 440 years 14 400 years 1 440 years 17 280 years
Tretā ³⁄₁₀ 1080 years 10 800 years 1080 years 12 960 years
Dvāpara ²⁄₁₀ 720 years 7 200 years 720 years 8 640 years
Kali ¹⁄₁₀ 360 years 3 600 years 360 years 4 320 years

Yugas, based on Hebrew Astrology by Sepharial, ¹²⁄₁₂ version 2
Sandhyā ¹⁄₁₂ Yuga ¹⁰⁄₁₂ Sandhyānśa ¹⁄₁₂ ∑ (sum) ¹²⁄₁₂
∑ (sum) ¹⁰⁄₁₀ 4 320 years 43 200 years 4 320 years 51 840 years
Kṛta|Satya ⁴⁄₁₀ 1 728 years 17 280 years 1 728 years 20 736 years
Tretā ³⁄₁₀ 1 296 years 12 960 years 1 296 years 15 552 years
Dvāpara ²⁄₁₀ 864 years 8 640 years 864 years 10 368 years
Kali ¹⁄₁₀ 432 years 4 320 years 432 years 5 184 years

Yugas based on Hebrew Astrology by Sepharial, ²⁷⁄₂₇ version 1
Sandhyā ¹⁄₂₇ Yuga ²⁵⁄₂₇ Sandhyānśa ¹⁄₂₇ ∑ (sum) ²⁷⁄₂₇
∑ (sum) ¹⁰⁄₁₀ 1 600 years 40 000 years 1 600 years 43 200 years
Kṛta|Satya ⁴⁄₁₀ 640 years 16 000 years 640 years 17 280 years
Tretā ³⁄₁₀ 480 years 12 000 years 480 years 12 960 years
Dvāpara ²⁄₁₀ 320 years 8 000 years 320 years 8 640 years
Kali ¹⁄₁₀ 160 years 4 000 years 160 years 4 320 years

Yugas based on Hebrew Astrology by Sepharial, ²⁷⁄₂₇ version 2
Sandhyā ¹⁄₂₇ Yuga ²⁵⁄₂₇ Sandhyānśa ¹⁄₂₇ ∑ (sum) ²⁷⁄₂₇
∑ (sum) ¹⁰⁄₁₀ 1 728.0 years 43 200 years 1 728.0 years 46 656.0 years
Kṛta|Satya ⁴⁄₁₀ 691.2 years 17 280 years 691.2 years 18 662.4 years
Tretā ³⁄₁₀ 518.4 years 12 960 years 518.4 years 13 996.8 years
Dvāpara ²⁄₁₀ 345.6 years 8 640 years 345.6 years 9 331.2 years
Kali ¹⁄₁₀ 172.8 years 4 320 years 172.8 years 4 665.6 years

…

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