“Calculating by the secret period of the Great Neros and the Hindu Kalpas, some kabalists, mathematicians and archeologists who knew naught of the secret computations made the above number of 21,000 years to be 24,000 years, for the length of the great year, as it was to the renewal only of our globe that they thought the last period of 6,000 years applied.
Higgins gives as a reason for it, that it was anciently thought that the equinoxes preceded only after the rate of 2,000, not 2,160, years in a sign; for thus it would allow for the length of the great year four times 6,000 or 24,000 years.
“Hence”, he says, “might arise their immensely-lengthened cycles; because, it would be the same with this great year as with the common year, till it traveled round an immensely-lengthened circle, when it would come to the old point again.”
He therefore accounts for the 24,000 in the following manner: “If the angle which the plane of the ecliptic makes with the plane of the equator had decreased gradually and regularly, as it was till very lately supposed to do, the two planes would have coincided in about ten ages, 6,000 years; in ten ages, 6000 years more, the sun would have been situated relatively to the Southern Hemisphere as he is now to the Northern; in ten ages, 6,000 years more, the two planes would coincide again; and, in ten ages, 6,000 years more, he would be situated as he is now, after a lapse of about twenty-four or twenty-five thousand years in all.
When the sun arrived at the equator, the ten ages or six thousand years would end, and the world would be destroyed by fire; when he arrived at the southern point, it would be destroyed by water.
And thus it would be destroyed at the end of every 6,000 years, or ten neroses.””
H. P. Blavatsky