Mahavira’s nirvana (veer nirvan) is traditionally described as occurring at Pawapuri. The clearest conventional time given in Jain texts is that it happened at dawn on the night of Kartik Amavasya (the new moon night), by which time the soul is said to have attained moksha. In some digests and recensions there are small variations about the exact night, but the common authoritative line in Kalpasutra-based tradition is: the nirvana occurred at dawn on the amavasya night of Kartik. So, the precise time cited in standard Jain accounts is dawn on Kartik Amavasya night. ( jainknowledge.com)

If you’d like, I can summarize how this timing is described in the Śvetāmbara Kalpasutra versus Digambara texts, with the minimal differences kept clear.