Pakhi in Jain Dharma means Pakshik Pratikraman — the fortnightly repentance and आत्मशुद्धि practice.

• It is generally done once in every 15 days
• Usually on Chaturdashi or the Pakshik day according to the Jain calendar
• It is a time for self-review, repentance, and cleansing of faults

If you mean Pakhi dates for April, those depend on the Jain Panchang and the sect/tradition followed.