SB 10.13.40
tavad etyatmabhur atma-
manena truty-anehasa
purovad abdam kridantam
dadrse sa-kalam harim
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
When Lord Brahma returned after a moment of time had passed (according to his own measurement), he saw that although by human measurement a complete year had passed, Lord Krsna, after all that time, was engaged just as before in playing with the boys and calves, who were His expansions.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Lord Brahma had gone away for only a moment of his time, but when he returned, a year of human time had passed. On different planets, the calculation of time is different. To give an example, a man-made satellite may orbit the earth in an hour and twenty-five minutes and thus complete one full day, although a day ordinarily takes twenty-four hours for those living on earth. Therefore, what was but a moment for Brahma was one year on earth. Krsna continued to expand Himself in so many forms for one year, but by the arrangement of yoga-maya no one could understand this but Balarama.
After one moment of Brahma’s calculation, Brahma came back to see the fun caused by his stealing the boys and calves. But he was also afraid that he was playing with fire. Krsna was his master, and he had played mischief for fun by taking away Krsna’s calves and boys. He was really anxious, so he did not stay away very long; he came back after a moment (of his calculation). When Brahma returned, he saw that all the boys, calves and cows were playing with Krsna in the same way as when he had come upon them; by Krsna’s display of yoga-maya, the same pastimes were going on without any change.
On the day when Lord Brahma had first come, Baladeva could not go with Krsna and the cowherd boys, for it was His birthday, and His mother had kept Him back for the proper ceremonial bath, called santika-snana. Therefore Lord Baladeva was not taken by Brahma at that time. Now, one year later, Brahma returned, and because he returned on exactly the same day, Baladeva was again kept at home for His birthday. Therefore, although this verse mentions that Brahma saw Krsna and all the cowherd boys, Baladeva is not mentioned. It was five or six days earlier that Baladeva had inquired from Krsna about the extraordinary affection of the cows and cowherd men, but now, when Brahma returned, Brahma saw all the calves and cowherd boys playing with Krsna as expansions of Krsna, but he did not see Baladeva. As in the previous year, Lord Baladeva did not go to the woods on the day Lord Brahma appeared there.