In The Name of Allaah, The Most Merciful, The Bestower of Mercy
Imaam Abdul Azeez Bin Baaz (rahimahullaah) stated that it has been transmitted in some of the narrations by Imaam Muslim (rahimahullaah) that it is the time when the Imaam sits on the Minbar on the Day of Jumu’ah up until the Salaah finishes. This is what has been transmitted in the hadeeth of Abu Moosaa (radiyallaahu-anhu). It has also been transmitted in the hadeeth of Jaabir Bin Abdillaah and Abdullaah Bin Salaam (radiyallaahu-anhumaa) that it is time period after Asr prayer up until sunset. And it has also been transmitted in some Ahaadeeth that it is the last hour on the day of Jumu’ah. All these statements are correct and they do not negate one another. And what is more explicit and more expected is that it is between the time when the Imaam sits on the Minbar up until the end of the prayer and the time between after Asr prayer up until sunset – these two time periods are more expected to be the periods during which supplication is accepted. And throughout the day of Jumu’ah, it is hoped that supplications are answered; but the most expected times are the times between when the Imaam sits on the Minbar until the end of the prayer and after Asr prayer until sunset. So it is befitting that one increases in making supplication on the day of Jum’ah, but it is befitting that one gives more concern in seeking after those three time periods that have been mentioned because the Messenger (sallal-laahu-alayhi-wasallam) stated that they are the times in which supplication is answered.
[Fataawaa Shaikh Ibn Baaz 12/401-402 (Paraphrased & abridged)] http://www.albaidha.net/vb4/showthread.php?t=15141