After mother Sita entered the earth (video)
Srimad Bhagavatam class by HH Subhag Swami in Mayapur, Jan 22, 2019.
HH Subhag Swami Maharaj on Srimad Bhagavatam 9.11.18-19 Text 18: After mother Sītā entered the earth, Lord Rāmacandra observed complete celibacy and performed an uninterrupted Agnihotra-yajña for thirteen thousand years.
Watch it here: https://goo.gl/ENzQ5W