How are Makkan and Madinan surahs determined, and what is the adopted criterion for that, especially regarding surahs that included verses revealed during different periods, or those whose classification scholars have differed upon?

Scholars have devoted attention to knowing what is Meccan and what is Medinan in the Qur’an. The most preponderant opinion is that whatever was revealed before the Hijra is Meccan, and whatever was revealed after it is Medinan, even if the place of revelation differed. Thus, the verse “Indeed, Allah commands you to render trusts” is Medinan despite its revelation in Mecca on the Day of Conquest, and “This day I have perfected for you your religion” is Medinan despite its revelation in Arafat, because their revelation was after the Hijra. The description of a surah as Meccan or Medinan does not mean that all its verses are likewise, for a Meccan surah may contain Medinan verses and vice versa. The reason for the difference in classifying some surahs is due to the difference in determining their time of revelation, whether it was before or after the Hijra.