What does the Atharva Veda say about the calculation of yugas?

Śataṁ te'ayutaṁ hāyanāndre yuge trīṇi catvāri kṛṇmaḥ।
Indrāgnī viśve devās te'anu manyantām ahṛṇīyamānāḥ॥

- Atharvaveda (8.2.21)

Oh child, I can turn 100 years of your age into a thousand years, a thousand years into two Yugas, two Yugas into three Yugas, and three Yugas into four Yugas. The Indra, Agni, and Vishwa Dev(devtas) should accept this prayer without any shame or anger.

That is, it is in the power of Param Brahma Parmatma that he can increase or decrease the age of any Yuga and everyone will have to accept it.