When is it permissible to give out Zakat al-Fitr for it to be valid, and does the time of its distribution differ with the varying number of days in Ramadan, and is it permissible to give it out on the eve of Eid before the Fajr prayer?

Zakat al-Fitr is considered valid if a person pays it after sunset on the the twenty-seventh day, in case the month has thirty days. This is because Ibn Umar used to send it two or three days before Eid al-Fitr. It is even more appropriate if it is paid on the eve of Eid. The best time to pay it is on the day of Eid, after the Fajr prayer and before going to the musalla (prayer ground).