It is well known in Sanathan dharma that the universe we exist in is the creation of Brahma through his manas and hence we call him 'samisthi Jiva'. The experience of time is different for humans and Brahma. The following statements are useful in understanding this
The learned say that these twelve thousand years (of the deities) constitute what is called a yuga. A thousand such yugas compose a single day of Brahman. The same is the duration of Brahman's night. With the commencement of Brahman's day the universe begins to start into life. During the period of universal dissolution the Creator sleeps, having recourse to yoga-meditation. When the period of slumber expires, He awakes. That then which is Brahman's day extends for a thousand such yugas. His nights also extends for a thousand similar yugas. They who know this are said to know the day and the night. On the expiry of His night, Brahman, waking up, modifies the indestructible chit by causing it to be overlaid with Avidya. He then causes Consciousness to spring up, whence proceeds Mind which is identical with the Manifest.
This question is not about the time spans. But about the existence of time and the perceiver of time. It is known that the sixth organ, the manas, is responsible for the perception or experience of time. So, humans don't experience time during Sushupthi/deep sleep. Time does exist only during waking/Jagrut and Swapna/dream state. Although time does not exist to a human during her Sushupthi, other humans, Brahma, pitrus, devtas experience time since their manas is active.
But when Brahma goes into yogic sleep then who experiences the time and how can one calculate the sleep time is the same as the daytime of Brahma? As I told before if a human is in a deep sleep state, she does not experience time but other persons can experience time if they are awake or dreaming and hence they have the perception of time. Is it the same case with Brahma? Since there are infinite Brahmas, even if a Brahma is sleeping, time continues to exist for other Brahmas who may be continuing their creations in a wake-up state? Or is there anything I need to consider?