The earliest text to mention 527 BCE as the year of Mahavira's nirvana is Yati-Vrishabha's Tiloya-Pannatti (6th century CE).
[3] On 21 October 1974, the 2500th Nirvana Mahotsava was celebrated (according to the Indian national calendar) by Jains throughout India[4] and overseas.
For example, The Vira Nirvana Samvat 2544 started right after Diwali of 20 October 2017 on Vikram 2074, Kartika Krishna Amavasya (Chaitradi and Purnimanta).
[6][7] The new Chaitradiadi Vikram samvat (common in North India) starts seven months earlier in Chaitra, thus during Chaitra-Kartika Krishna, the difference between Vikram and Vir Nivana samvat is 469 years until Kartik Shukla 1 (Day following Diwali), when the difference becomes 470 years.
The months in a Jain calendar are – Kartak, Maagsar, Posh, Maha, Faagan, Chaitra, Vaishakh, Jeth, Ashadh, Shravan, Bhadarvo, Aaso.