Is it permissible to give out all or some of the Zakat before its due date (Hawl)?

It is permissible to pay Zakat before its due time, as the Prophet, peace and blessings be upon him, advanced Zakat for two years from Al-Abbas ibn Abd al-Muttalib. It must be noted that the obligation of Zakat upon the completion of a full year (hawl) is based on the Hijri year, not the Gregorian year.