The Second Buddhist Council was held during the reign of

The Buddhist councils were periodic assemblies of monks convened after the Buddha's Mahaparinirvana to recite, preserve, and settle disputes over the canonical teachings (the Tripitaka); each council is tied to a specific ruler who provided royal patronage and to the place where it met.

The Second Buddhist Council was held about a century after the Buddha's death, at Vaishali, to settle a dispute over ten points of monastic discipline (the "ten indulgences") that a group of Vajjian monks had begun following. This council met under the patronage of King Kalashoka (also called Kakavarnin), a ruler of the Shishunaga dynasty who governed Magadha from the capital Pataliputra -- placing the council squarely within his reign.

• Shishunaga founded the dynasty that bears his name and reigned well before this council's traditional date, so his reign does not match.

• Mahapadmananda founded the Nanda dynasty, which rose to power only after the Shishunaga line had run its course, so his reign comes later, not at the time of this council.

• Udayabhadra (Udayin) belonged to the earlier Haryanka dynasty, as the successor of Ajatashatru, and is remembered for shifting the capital to Pataliputra -- this predates even the rise of the Shishunaga dynasty under which this council was later held.

Because the Second Buddhist Council's traditional date and venue align only with Kalashoka's rule over Magadha, that is the reign in which it was held.