We find that many books on salat state the ending time of the Zuhr prayer and the starting time of the Asr prayer when the shadow of something is twice itself especially the books which are written by the followers of the Hanafi school of thought.
But this contradicts the above hadith as on the first day Jibreel asked Prophet Muhammad (s) to pray Asr when the shadow of everything was equal to itself. This means that was the end time of Zuhr prayer. And we already know that all the ulamas of the Muslim Ummah agree unanimously that no prayer can be offered before its time.
Imam Abu Hanifa (Rahmatullah Alai) is reported to have changed his opinion before he passed away, and prayed his Asr prayer according to the time stated in this hadith. His two students, Imam Abu Yusuf and Imam Muhammad, used to give Fatwas for the time of Asr prayer according to this hadith, too.
(Fatawa Azeeziah, Fatawa Rasheediah)