Islam follows a lunar calendar. Obviously, the month changes at the site of first crescent of the new moon and this happens only at sunset. It therefore implies that a date too should change at sunset. This methodology is followed universally in Islam.
I could find this hadith that indirectly backs up this methodology:
Once the people doubted the appearance of the moon of Ramadan, and intended neither to offer the tarawih prayer nor to keep fast. A bedouin came from al-Harrah and testified that he had sighted the moon. He was brought to the Prophet (ﷺ). He asked: Do you testify that there is no god but Allah, and that I am the Messenger of Allah? He said: Yes; and he testified that he had sighted the moon. He commanded Bilal who announced to the people to offer the tarawih prayer and to keep fast.
In another hadith (Sahih), The Holy Prophet (ﷺ) calls the 'Asr prayer 'middle prayer'
Narrated Samurah bin Jundab:
"The Prophet of Allah (ﷺ) said: 'The middle Salat is Salat Al-'Asr.'"
When the day is believed to be commenced with the sunset, the Maghrib prayer should be the first prayer and 'Asr should be the last prayer and the middle prayer should actually be Fajr.
Why then is 'Asr prayer called the middle prayer?
If it is a different context that the hadith refers to, what is that context and how does it make 'Asr the middle prayer?
I stumbled upon another hadith:
Zaid b. Thabit said:
The Messenger of Allah (ﷺ) used to offer the Zuhr prayer in midday heat; and no prayer was harder on the Companions of the Messenger of Allah (ﷺ) that this one. Hence the revelation came down: "Be guardians of your prayers, and of the midmost prayer" (2:238). He (the narrator) said: There are two prayers before it and two prayers after it.
In this hadith, the Zuhr prayer is called the mid-most prayer. It is also mentioned that there are two prayers before it and two prayers after it. Now again, two more questions arise.
- How is this Hadith compatible with the previous hadith that mentions 'Asr as the middle prayer?
- Two prayers before Zuhr means Isha and Fajr. Does the hadith also mean that the next date actually starts after Maghrib (ie. with 'Isha)?