Krishna says:

By human calculation, a thousand ages taken together form the duration
of Brahma's one day (4,32 billion years). And such also is the
duration of his night. (Bg. 8.17)

At the beginning of Brahma's day, all living entities become manifest
from the unmanifest state, and thereafter, when the night falls, they
are merged into the unmanifest again. (Bg. 8.18)

Again and again, when Brahma's day arrives, all living entities come
into being, and with the arrival of Brahma's night they are helplessly
annihilated. (Bg. 8.19)

Yet there is another unmanifest nature, which is eternal and is
transcendental to this manifested and unmanifested matter. It is
supreme and is never annihilated. When all in this world is
annihilated, that part remains as it is. (Bg. 8.20)

That which the Vedantists describe as unmanifest and infallible, that
which is known as the supreme destination, that place from which,
having attained it, one never returns—that is My supreme abode.
(Bg. 8.21)

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