Calculation of Time is started from a special event and this gives birth of calendars. In Indian tradition the calculation of time starts from the time when the universe was created.
According to Indian ancient scriptures, Brahma, the creator, creates and destroys the universe cyclically. The life of Brahma is 120 divine years called Mahakalpa. Every day he creates 14 Manus one by one and they create and control the world. So there are fourteen Manus in one divine day called Kalpa of Brahma.
There are many calculations which depict / represent many theories though I would like to show them all in one table.
Krati = 34,000th of a second
1 Truti = 300th of a second
2 Truti = 1 Luv
2 Luv = 1 Kshana
30 Kshana = 1 Vipal
60 Vipal = 1 Pal
60 Pal = 1 Ghadi (24 minutes)
2.5 Gadhi = 1 Hora (1 hour)
24 Hora = 1 Divas (1 day)
7 Divas = 1 saptaah (1 week)
4 Saptaah = 1 Maas (1 month)
2 Maas = 1 Rutu (1 season)
6 Rutu = 1 Varsh (1 year)
100 Varsh = 1 Shataabda (1 century)
10 Shataabda = 1 sahasraabda
432 Sahasraabda = 1 Yug (Kaliyug)
2 Yug = 1 Dwaaparyug
3 Yug = 1 Tretaayug
4 Yug = 1 Krutayug
10 Yug = 1 Mahaayug (4,320,000 years)
1000 Mahaayug = 1 Kalpa
1 Kalpa = 4.32 billion years
In terms of years
SATYUG 4,32,000 YEARS X 4 = 17,28,000 YEARS
TRETA 4,32,000 YEARS X 3 = 12,96,000 YEARS
DWAPAR 4,32,000 YEARS X 2 = 8,64,000 YEARS
KALIYUG 4,32,000 YEARS X 1 = 4,32,000 YEARS
1 MAHAYUG (GRAND TOTAL OF ALL THE YUGAS) = 4,320,000 YEARS
71 MAHAYUG = 43,20,000X71 = 1 MANVANTAR
1 MANVANTAR = 30,6720,000 YEARS
14 MANVANTAR = 4,294,080,000 YEARS
Let’s see the age of our cosmos as per the Vedic System.
There are 14 Manvantaras altogether. The present period is passing through the seventh Manvantara called Vaivaswata Manvantara.
One Manvantara = 71 Mahayugs (out of which 27 Mahayugs have already passed)
The time period of Manvantara (exclusive period, when the earth is submerged in water, in the beginning and in the end) = 306,720,000 years
Multiplying these years by 6 = 30,67,20,000 x 6 = 1,8,0,300,000 years
(Because we are in the midst of 7th Manvantara, of the Svetvaaraah Kalpa and 6 Manvantaras have already passed)
The time period of Pralaya consists of 17,28,000 years since 7 Pralayas have passed, after the end of 6th Kalpa and before the beginning of 7th Kalpa, so
Total Pralaya Time = 17,28,000 x 7 = 12,096,000 years
Total Passed Years = 1,840,300,000 + 120 96 000 = 1,852,396,000 years
Therefore, after 1,85,24,16,000 years ‘VAIVASVAT MANVANTARA’ has started.
27 Mahayugs with each Mahayuga consisting of 43,20,000 years. 43,20,000 x 27 = 116,640,000 years have passed
Total Passed Years = 1,852,396,000 + 116,640,000 = 1,96,90,56,000 years
Now the time period of Kali Yuga in the 28th Yuga
Time period of Satya Yuga = 17,28,000
Time period of Treta = 12,96,000
Time period of Dwapar = 8,64,000
TOTAL = 38,88,000
Since all the above three Yugas have already passed, it means that after 38, 88,000 years, Kali Yuga came into existence.
Total Passed Years = 1,96,90,56,000 + 38, 88,000 = 1,97,29,44,000
Years Kali Yuga started on Bhadrapada, Krishnapaksha -13th day, in Vyatipaat yoga at midnight, in the Aashlesha Nakshatra and the age of the Kali Yuga has been fixed as 5111 years as till date that is Vikram Samvat 2065 = Shaka 1932 = 2000 AD.
Sum of all the three Yugs = the Sum of 27 Mahayugas and Manvantar + the time period of Kali Yuga till date.
Total Passed Years = 1,97,29,44,000 + 1,97,29,49,111
Years Kalpa consist of 4,32,00,00,000 years and out of these 1,97,29,49,101 years have passed.
Therefore, the earth’s existence, according to the calculations devised by our ancient sages, comes up to 1,97,29,49,111 years till date.
It is interesting to note that according to scientific calculations, the age of the cosmos is estimated between 15 and 20 billion years.
Sources: http://www.astrojyoti.com