Sri Chaitanya Mahaprabhu disappeared at Jagannatha Puri in June 1534. Within a few years Advaita Acharya, Srivasa Pandit and most of the first generation of the Nabadwip devotees had followed Him. Nityananda Prabhu, who had spent the last twenty-odd years of the Lord's manifest life in Bengal rather than in Puri, outlived them all by a short margin, and then went himself, at some point around 1540.
The date cannot be fixed. This is not evasiveness; it is the honest state of the record, and the reason for it is worth understanding. The two great biographies both fail us here, and they fail us for opposite reasons. Vrindavana Dasa Thakura's Chaitanya-bhagavata was written in Nityananda Prabhu's own lifetime and, according to Krishnadasa Kaviraja, by his order; it necessarily ends before his disappearance. Krishnadasa Kaviraja's Chaitanya-charitamrita was written half a century later, in Vrindavana, and it is a life of Chaitanya Mahaprabhu; it records Nityananda's activities where they bear on the Lord's and simply does not narrate his passing. Nothing comparable to the detailed Puri accounts of Mahaprabhu's own disappearance was ever written for him. What survives is temple tradition, later Bengali hagiography, and the genealogies, and they diverge.
Most modern accounts settle on about 1540. The Vaishnava-digdarsini gives 1542, and makes him sixty-nine years old at the time, which fits an appearance in 1473. Some sources give as late as 1544; a few place it as early as 1533, which is difficult to reconcile with other events. Where a range of ten years exists for a man about whom a substantial devotional literature was written within living memory, the sensible course is to say around 1540 and leave it there.
The place and manner are contested in a more interesting way, because two quite different accounts have come down, each attached to a real location.
The account that most Gaudiya Vaishnavas hold, and the one attached to a place people still visit, puts it at Ekachakra. In this version he travelled back to the village of his birth in Birbhum, in some tellings taking Jahnava Devi with him to show her where he had come from, and there he merged into the Deity of Banka Raya. Banka Raya, also called Bankima Raya, is a form of Krishna which, according to the priests of Ekachakra, Nityananda Prabhu had himself recovered from the water at the Kadamba-khandi ghat as a boy and installed in the village. The priests of the temple describe the disappearance in exactly those terms, and add the detail that gives the account its internal coherence: it was after this that the deity of Jahnava Mata was placed at Banka Raya's right-hand side, where she stands to this day. The Bhakti-ratnakara supports the Ekachakra version, and Srila Prabhupada records the temple tradition in his purport on Ekachakra in the Adi-lila.
The other account puts it at Khardaha, on the Ganges north of Calcutta, where he had lived for the last part of his life, and says that he disappeared during kirtana in the temple of Shyamasundara there. The objection raised against this version is chronological rather than devotional: the Shyamasundara Deity at Khardaha is generally held to have been installed later than 1540, which makes it hard to sustain the story in that precise form. Variants exist which place the event at Khardaha without naming that Deity. Some traditions attach it to the death of Vasudha; others simply record that he passed at Khardaha and are silent about the manner.
There is no honest way to choose between them from the outside, and the tradition has not really tried. What can be said is that this sort of divergence is entirely normal for the period and the subject. The disappearance of Chaitanya Mahaprabhu Himself is described with deliberate reticence by every one of His biographers and remains one of the most discussed questions in Gaudiya history. The word used throughout is disappearance rather than death, and the accounts that survive are theological statements as much as topographical ones. To say that he merged into the Deity of Banka Raya is, in the tradition's own idiom, to say something about where he now is rather than to report the disposal of a body: the claim is that he is present in that Deity, which is why people go there. A reader who wants a coroner's account of the death of Nityananda Prabhu will not find one, and the reason is that nobody who wrote about him was interested in producing one.
What can be established, and what the tradition is unanimous about, is what he left behind, and it is a great deal.
He left Bengal organised. The eleventh chapter of the Adi-lila names more than seventy-five branch leaders of his line, twelve of them identified as the cowherd boys of Vraja returned, and Krishnadasa Kaviraja's summing-up is that each of them had the independent strength to give love of Krishna to whomever they met. The householder congregations at Khardaha, Panihati, Saptagram, Ambika Kalna and across the Birbhum country were his work. So was the reintegration of the suvarna-vanik community, which had been outside respectable Hindu society in Bengal for centuries until he went and ate in Uddharana Datta Thakura's house at Saptagram.
He left a family. Virabhadra Gosani, his son by Vasudha, is described by Krishnadasa Kaviraja as the topmost branch of the line and the main pillar of the whole edifice of devotional service, and it is Virabhadra who built the temple at Ekachakra that his father had never bothered to build. And he left Jahnava Mata, whose leadership over the second generation, culminating in her presidency of the festival at Kheturi, is the single reason the movement did not come apart in the decades when all its founders died within a few years of each other.
He left, at one remove, both of the movement's principal books. The Chaitanya-bhagavata was written by Vrindavana Dasa Thakura on his order, and Krishnadasa Kaviraja notes as much: by Nityananda Prabhu's order and strength, Vrindavana Dasa described elaborately everything that he himself had left out. And the Chaitanya-charitamrita exists because Nityananda Prabhu appeared in a dream to a quarrelsome Bengali householder at Jhamatpura, put His feet on his head, and told him to go to Vrindavana, where he would attain everything. He went, met Rupa Goswami's successors, and wrote the book. Gaudiya Vaishnavism's two central biographies of its founder are thus, in different ways, both his.
Ekachakra today is called Birchandrapur, after his son, and lies in Birbhum district in West Bengal. The site of the birth, Garbhavasa, is maintained; the Banka Raya temple stands half a mile away with Radharani on one side and Jahnava Mata on the other, rebuilt after lightning struck it in 1924; the ancient bakula tree is shown, and the tank at Hantugada, and the spot called Visramatala where he is said to have staged the Vraja pastimes with the village boys. Large fairs are still held there on his appearance day and at Goshthashtami.
Perhaps the most characteristic thing about the tradition's handling of his disappearance is how little difference it is felt to have made. Jahnava Mata is said to have continued receiving his guidance for the rest of her life. The doctrine of his mercy, set out on the mercy of Nitai, is stated in the present tense and always has been; Krishnadasa Kaviraja, writing perhaps fifty years after the event, describes what Nityananda did for him personally as something ongoing. And in practice, the deities installed in Gaudiya temples make the point without arguing it: Chaitanya Mahaprabhu is not installed alone. Nityananda Prabhu stands beside Him, arms raised, exactly as he did in the streets of Nabadwip, and Bengali Vaishnavas still put his name first when they greet each other.