Diwali has a very special significance in Jainism, just like Buddha Purnima, the date of Buddha's Nirvana, is for Buddhists as Christmas is for Christians. Lord Mahavira, the last of the Jain Tirthankaras, attained Nirvana or Moksha on this day at Pavapuri on Oct. 15, 527 BC, on Chaturdashi of Kartika, as Tilyapannatti of Yativrashaba from the sixth century states:
Mahavira is responsible for establishing the Dharma followed by Jains even today. According to tradition, the chief disciple of Mahavira, Ganadhara Gautam Swami also attained complete knowledge (Kevalgyana) on this day, thus making Diwali one of the most important Jain festivals.
Mahavira attained his nirvana at the dawn of the amavasya (new moon). According to the Kalpasutra by Acharya Bhadrabahu, 3rd century BC, many gods were present there, illuminating the darkness. The following night was pitch black without the light of the gods or the moon. To symbolically keep the light of their master's knowledge alive:
16 Gana-kings, 9 Malla and 9 Lichchhavi, of Kasi and Kosal, illuminated their doors. They said: "Since the light of knowledge is gone, we will make light of ordinary matter" ("गये से भवुज्जोये, दव्वुज्जोयं करिस्समो").
Dipavali was first mentioned in Jain books as the date of the nirvana of Mahavira. In fact, the oldest reference to Diwali is a related word, dipalikaya, which occurs in Harivamsha-Purana, written by Acharya Jinasena  and composed in the Shaka Samvat era in the year 705.
ततस्तुः लोकः प्रतिवर्षमादरत् प्रसिद्धदीपलिकयात्र भारते |
समुद्यतः पूजयितुं जिनेश्वरं जिनेन्द्र-निर्वाण विभूति-भक्तिभाक् |२० |
tatastuh lokah prativarsham-araat ako
samudyatah poojayitum jineshvaram
Translation: The gods illuminated Pavanagari by lamps to mark the occasion. Since that time, the people of Bharat celebrate the famous festival of "Dipalika" to worship the Jinendra (i.e. Lord Mahavira) on the occasion of his nirvana.
Dipalikaya roughly translates as "light leaving the body". Dipalika, which can be roughly translated as "splenderous light of lamps", is used interchangeably with the word "Diwali".
The way Jains celebrate Diwali is different in many respects. There is a note of asceticism in whatever the Jains do, and the celebration of Diwali is not an exception. The Jains celebrate Diwali during the month of Kartik for three days. During this period, among the Shvetambaras, devoted Jains observe fasting and chant the Uttaradhyayan Sutra, which contain the final pravachans of Lord Mahavira, and meditate upon him. Some Jains visit Pavapuri in Bihar where he attained Nirvan. In may temples special laddus are offered particularly on this day.
Vira Nirvana Samvat: The Jain year starts with Pratipada following Diwali. Vira Nirvana Samvat 2536 starts with Diwali 2009. The Jain businesspeople traditionally started their accounting year from Diwali. The relationship between the Vir and Shaka era is given in Titthogali Painnaya and Dhavalaa by Acharya Virasena:
पंच य मासा पंच य वास छच्चेव होन्ति वाससया|
परिणिव्वुअस्स अरिहितो तो उप्पन्नो सगो राया||
Thus the Nirvana occurred 605 years and 5 months before the Saka era.
On 21 October 1974 the 2500th Nirvana Mahotsava was celebrated by all the Jain throughout India.