Iftaar Time (Ahadith 1670 - 1674)

Bismillah.
Volume 3, Book 31, Number 175:
Narrated Umar bin Al-Khattab (radiallaahu `anhu):
Allah's Apostle (sallallaahu `alayhi wasallam) said, "When night falls from this side and the day vanishes from this side and the sun sets, then the fasting person should break his fast."

Volume 3, Book 31, Number 176:
Narrated Abdullah bin Abi Aufa (radiallaahu `anhu):
We were in the company of the Prophet (sallallaahu `alayhi wasallam) on a journey and he was fasting, and when the sun set, he addressed somebody, "O so-and-so, get up and mix Sawiq with water for us." He replied, "O Allah's Apostle (sallallaahu `alayhi wasallam)! (Will you wait) till it is evening?" The Prophet (sallallaahu `alayhi wasallam) said, "Get down and mix Sawiq with water for us." He replied, "O Allah's Apostle (sallallaahu `alayhi wasallam)! (If you wait) till it is evening." The Prophet (sallallaahu `alayhi wasallam) said again, "Get down and mix Sawiq with water for us." He replied, "It is still daytime." The Prophet (sallallaahu `alayhi wasallam) said again, "Get down and mix Sawiq with water for us." He got down and mixed Sawiq for them. The Prophet (sallallaahu `alayhi wasallam) drank it and then said, "When you see night falling from this side, the fasting person should break his fast."

Volume 3, Book 31, Number 177:
Narrated 'Abdullah bin Abi Aufa (radiallaahu `anhu):
We were traveling with Allah's Apostle (sallallaahu `alayhi wasallam) and he was fasting, and when the sun set, he said to (someone), "Get down and mix Sawiq with water for us." He replied, "O Allah's Apostle (sallallaahu `alayhi wasallam)! (Will you wait) till it is evening?" The Prophet (sallallaahu `alayhi wasallam) again said, "Get down and mix Sawiq with water for us." He replied, "O Allah's Apostle (sallallaahu `alayhi wasallam)! It is still daytime." The Prophet (sallallaahu `alayhi wasallam) said again, "Get down and mix Sawiq with water for us." So, he got down and carried out that order. The Prophet (sallallaahu `alayhi wasallam) then said, "When you see night falling from this side, the fasting person should break his fast," and he beckoned with his finger towards the east.

Volume 3, Book 31, Number 178:
Narrated Sahl bin Sad (radiallaahu `anhu):
Allah's Apostle (sallallaahu `alayhi wasallam) said, "The people will remain on the right path as long as they hasten the breaking of the fast."
Al-Nawawi said: 
This hadeeth means that we are encouraged to hasten to break the fast after ascertaining that the sun has indeed set. What this means is that the ummah’s affairs will continue to be in order and they will be fine so long as they adhere to this Sunnah. But if they delay breaking the fast, that will be an indication of some misguidance that they are following. 
Sharh Muslim, 7/208

Volume 3, Book 31, Number 179:
Narrated Ibn Abi Aufa (radiallaahu `anhu):
I was with the Prophet (sallallaahu `alayhi wasallam) on a journey, and he observed the fast till evening. The Prophet (sallallaahu `alayhi wasallam) said to a man, "Get down and mix Sawiq with water for me." He replied, "Will you wait till it is evening?" The Prophet (sallallaahu `alayhi wasallam) said, "Get down and mix Sawiq with water for me; when you see night falling from this side, the fasting person should break his fast."
The Sunnah is to hasten to break the fast, which means breaking fast straight after the sun has set. Delaying the fast until after the stars have come out is the practice of the Jews, and the Raafidis (Shi’ah) followed them in that, So it is not correct to delay it deliberately until later in the evening or to delay it until the end of the adhaan. All of that is contrary to the teachings of the Prophet (peace and blessings of Allaah be upon him).