Times of Salaah

Q: A book stated:

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)

Q: I wanted to know what is the earliest duration between exactly sunset and esha (1h15 minutes or 1h 20 minutes)?  The reason for asking this question is that there is a site called islamic finder that has salaah times which seems to be very accurate and wanted to use it.

Q: What is the latest one can start his Salaah in order that the salaah be considered as adaa'? If one starts his Salaah in the Salaah time, and during the salaah, the time ends, does the salaah get invalidated or does it count as qadha?

Q: My question relates to the times of Tahajud. When i was in madressah I was taught that we could read from just after 12am till about 15min before fajar salah. Recently I was told many different things regarding the times. What would be the right time to read Tahajud salah and the cut off time?

Q: What is the time of Zuhr Salaah?