According to Jain tradition:

• The Antariksh Parshwanath (floating) idol is believed to be 11,80,000 (11.8 lakh) years old,
• And it is said to belong to the time of the 20th Tirthankar, Bhagwan Munisuvrat Swami.

From a historical/recorded history point of view, the tirth itself is roughly 900–950 years old, but in Jain Dharma we refer to the idol’s śraddhā-pūrvak (faith-based) age as 11.8 lakh years.

You can read a simple story-based explanation here