It is recommended to start the Eid al-Adha prayer at the beginning of its time range and to delay the Eid al-Fitr prayer because the Prophet (peace be upon him) did that. People need to attend to their sacrifice after the prayer at Eid al-Adha, while the delay in Eid al-Fitr prayer helps a person who has not yet paid Zakat al-Fitr to pay it, as it must be paid up to immediately before the prayer.
