Pakshi (Pakkhi / Fortnightly) Pratikraman is not fixed to one English calendar date. It is fixed to the Jain lunar tithi.

General rule (for most Jain sanghs):

• Pakshi Pratikraman is done twice in every lunar month
• It is usually done on Chaturdashi (14th tithi) of:

- Shukla Paksh (bright half of the month) - Krishna Paksh (dark half of the month)

So, practically:

• You do Pakshi Pratikraman on every Chaudash (14th) – so about once every 15 days.
• The exact English dates change every month and every year, and also depend on your city/time‑zone.

Because of this, to know the exact dates:

• Check your local Jain panchāng / tithi calendar, or
• See the annual calendar published by your local Jain Sangh or temple (they usually mark “Chaudash / Pakshi Pratikraman” clearly).

Both Śvetāmbara and Digambara traditions:

• Accept Pakshik (fortnightly) Pratikraman as recommended for those who cannot do it daily.
• Keep it tied to the lunar fortnight, not a fixed English date; details of the vidhi (text and method) differ, but the timing principle is the same.

You can read a simple explanation of daily, Pakshik, Choumasi and Samvatsari Pratikraman here