Alms Tax: Becoming Muslim or Shia After Sunset
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 2012
If a disbeliever becomes Muslim after sunset on the eve of Eid al-Fiṭr, it is not obligatory for him to give zakāt al‑fiṭrah. However, if a Muslim who was not a Shia becomes a Shia after the moon is sighted, he must give fiṭrah.
-Ayatullah Sistani, Practical Laws of Islam, Alms Tax (Zakat)