The Surya Siddhanta

100 | 12000 | These figures refer to the total years in a Great Age or Mahayuga. However, there appears to be a contradiction here, as the measurements for these ages are given as 4,800; 3,600; 2,400; and 1,200 years. To resolve this, the text states: In the sixth part. This means that one-sixth of the total duration represents the sum of the two "twilight" periods—the dawn at the beginning and the dusk at the end.

Thus, for the measurements I have stated: 4,800; 3,600; 2,400; and 1,200; their sixth parts are 800; 600; 400; and 200 respectively. These figures represent the combined duration of the opening and closing twilights for each respective age. Half of each figure represents a single transition period Sandhikala (the 'junction' or transition period between two cosmic ages).

The individual transition periods at the start and end of each age are therefore 400, 300, 200, and 100 years. By subtracting these, the "pure" duration of the ages mentioned in other texts is revealed, excluding their twilights.

Therefore, there is no contradiction; my stated figures include the transition periods because they are inherently connected to and contained within their respective ages. // 17 //

Next, to determine the duration of a Kalpa (an eon, or a 'Day of Brahma'), the text explains the measurement of a Manvantara (the reign of a Manu, a progenitor of humanity) and its transition period:

"Seventy-one cycles of the ages" refers to seventy-one Mahayugas (Great Ages). In this context of "measured time," a Manvantara is the duration between the start of a Manu's reign and its completion. This is explained by those expert in the different divisions of time. When that Manu's reign reaches its conclusion, there is a transition period equal to the years of the Golden Age (Krita Yuga) original: "Kritabda-sankhya", meaning 4,800 divine years which manifests as a Jalaplava (a cosmic deluge or great flood).