In Jain time measurement:

• 1 pūrvāṅga = 84,00,000 (8.4 million) years
• 1 pūrva = 84,00,000 pūrvāṅga

So,

> 1 pūrva = 84,00,000 × 84,00,000 years > = 7.056 × 10¹³ years > = 70,560,000,000,000 years

You can read a short explanation here