Men with a poor fund of knowledge accept history of the world since the time of Buddha or since 600 BC and prior to this period all histories mentioned in the scriptures are calculated by them as imaginary stories. That is not a fact. All the stories mentioned in the Purāṇas and Mahābhārata etc. are actual history not only of this planet but also of the other millions of planets within the universe. Some times the history of planets beyond this world appear to such men of poor fund of knowledge, as some thing nonbelievable. But they do not know that different planets are not equal in all respects and as such some of the historical facts derived from other planets do not correspond with the experience of this planet. Considering the different situation of different planets as also time and circumstances, there is nothing wonderful in the stories of the Purāṇas, nor are they imaginary. We should always remember the maxim that one man's food is another man's poison. We should not therefore reject the stories and histories of the Purāṇas as imaginary. The great ṛṣis like Vyāsa had no business to put some imaginary stories in His literatures.
In the Śrīmad-Bhāgavatam such selected historical facts taken out from the histories of different planets have been depicted. It is therefore accepted by all the spiritual authorities as the Mahā-Purāṇa. Special significance of these histories is that they are all connected with activities of the Lord in a different time and atmosphere. Śrīla Śukadeva Gosvāmī is the topmost personality of all the self-realized souls and he accepted as subject matter of studies from his father Vyāsadeva. Śrīla Vyāsadeva is the great authority and the subject matter of Śrīmad-Bhāgavatam being equally important, he delivered the message first to his great son Śrīla Śukadeva Gosvāmī. It is compared with the cream of the milk. Vedic literatures are like the Milk Ocean of knowledge. Cream or butter is the most palatable essence of milk and so also is Śrīmad-Bhāgavatam as it contains all palatable, instructive and authentic versions from different activities of the Lord and His devotees.
Srimad Bhagavatam 1.3.41, 1st printing in 1962,
commentary by AC Bhaktivedanta Swami
commentary by AC Bhaktivedanta Swami