Short answer

• In the Shwetambar tradition, Paryushan is set as an 8‑day period of intensified sadhana during Chaturmas, ending with Samvatsari (the great day of forgiveness).
• In the Digambar tradition, a related festival called Das‑Lakshan Parva is observed for 10 days.

Why “eight” days?

• Tradition, not a single historical event: The 8‑day span is an established Shwetambar convention for concentrated repentance, scriptural study (especially Kalpasutra pravachan), fasting, and pratikraman, culminating in universal forgiveness on day 8 (Samvatsari).
• Practical spiritual cycle: Eight continuous days allow laypeople to complete a full cycle of vows, austerities, and listening to discourses while monks/nuns are settled in one place during Chaturmas.
• Traditional associations: Many teachers connect the eight days with cultivating a set of core virtues—kshama (forgiveness), mardava (humility), arjava (straightforwardness), santosh/shauch (contentment/purity), satya (truth), samyam (self‑restraint), tap (austerity), and tyag (renunciation)—as a focused ladder toward inner purification before Samvatsari. This is a pedagogical emphasis within the Shwetambar tradition.

Digambar difference

• Digambar Jains observe 10 days as Das‑Lakshan Parva, each day dedicated to one of the ten supreme virtues; this is a separate, parallel practice to the Shwetambar 8‑day Paryushan.

For a simple explainer, see: and a day‑by‑day overview: