āsīt kalpa-kṣaye yathā
As Śrīla Viśvanātha Cakravartī Ṭhākura points out, the words atha and ekadā are commonly used in Sanskrit literature to introduce a new topic. Here they especially indicate that the reunion of the Yadus and Vṛṣṇis at Kurukṣetra is being narrated out of chronological sequence.
Śrīla Sanātana Gosvāmī explains in his Vaiṣṇava-toṣaṇī commentary that the events of this Eighty-second Chapter occur after Lord Baladeva’s visit to Vraja (Chapter 65) and before Mahārāja Yudhiṣṭhira’s Rājasūya sacrifice (Chapter 74). This must be so, the ācārya reasons, since during the eclipse at Kurukṣetra all the Kurus, including Dhṛtarāṣṭra, Yudhiṣṭhira, Bhīṣma and Droṇa, met in friendship and happily shared the company of Śrī Kṛṣṇa. At the Rājasūya-yajña, on the other hand, Duryodhana’s jealousy against the Pāṇḍavas became irrevocably inflamed. Soon after this, Duryodhana challenged Yudhiṣṭhira and his brothers to the gambling match, in which he cheated them of their kingdom and exiled them to the forest. Right after the Pāṇḍavas’ return from exile, the great Battle of Kurukṣetra took place, during which Bhīṣma and Droṇa were killed. So it is not logically possible for the solar eclipse at Kurukṣetra to have happened after the Rājasūya sacrifice.