It sounds like you’re asking about “Pakshi (Pakkhi) Pratikraman” and how much time it takes.

• How often: Pakshi/Pakkhi Pratikraman is done twice every lunar month (once in each fortnight).
• Typical duration:

- Shvetāmbara tradition: about 1.5 to 2 hours for the full traditional liturgy; shorter community versions may take around 60–90 minutes. - Digambara tradition: commonly about 60–90 minutes; fuller versions can be longer, depending on the sangh’s vidhi.

• Day it’s observed: usually on the 14th day (Chaturdashi) of each fortnight; local sangh schedules may vary slightly.

For simple guidance on when Pratikraman is done and the types (daily, Pakshi, Chaumasi, annual), see:

• When Pratikraman should be done
• Overview of Pratikraman types and frequency
• Pakkhi (fortnightly) timing note