In Jainism, the “first Tirthankar” is Bhagwan Rishabhdev (Ādināth).

Because Tirthankars lived in a very ancient part of the current time‑cycle, their age and dates are given in Jain cosmic time units, not in normal historical years.

How old was the first Tirthankar?

According to Jain scriptures and traditional Jain chronology:

• Bhagwan Rishabhdev’s lifespan was

8.4 million “purva” (a very, very huge time‑unit, far beyond normal years).

• In more “human” language: his life is described as lasting an unimaginably long time, many trillions of years.
• Among all 24 Tirthankars, Rishabhdev is described as the oldest in age and the tallest in height.

Both Śvetāmbara and Digambara traditions accept that:

• He lived for an extremely long span.
• Exact conversion into modern years is not the main point; the key idea is: Tirthankars are beings of a different, extraordinarily elevated era, not like present humans.

When was he born?

Again, this is given in Jain time‑cycle terms, not a “BC/CE” year.

Common traditional points (accepted in both sects, with minor calendar-variation):

• He is the first Tirthankar of the present Avasarpiṇī (descending half of time).
• He was born in Ayodhya (Vinītā) to

- Father: King Nābhirāja (Nabhi) - Mother: Queen Marudevī

• Many Śvetāmbara texts and Jain traditions state his Janma Kalyāṇak (birth) on:

Chaitra Krishna Navamī (9th day of dark half of month Chaitra).

• Some other traditions mention a different month (like Āṣāḍh Krishna), but all agree that:

- It was in the last part of the 3rd Ara (Suṣama‑Duṣamā) of the current descending time‑cycle. - It was millions of years ago, not within recorded human history.

You can read a simple explanation of how Ādeśwar/Ādināth became the first Tirthankar here