Fiqh-us-Sunnah Volume 3, Zakaat and Fasting, Fiqh 3.088B.

The jurists agree that zakat ul-fitr is due at the end of Ramadan. They differ, however, about the exact time.

Ath-Thauri, Ahmad, Ishaq, and ash-Shaf’i (in his later opinion), and Malik (in one of his reports) are of the opinion that it is due at the sunset of the night of breaking the fast, for this is when the fast of Ramadan ends. Abu Hanifah, al-Layth, ash-Shaf’i (in his original opinion), and the second report of Malik say that zakat ulfitr is due at the start of fajr on the day of ‘id.

These two different views acquire relevance if a baby is born after sunset but before dawn on the day of ‘id; the question then is whether zakat ul-fitr is obligatory for the baby or not. In accordance with the first view, it is not since the birth took place after the prescribed time, while according to the second view, it is due because the birth took place within the prescribed space of time.