The incident of the splitting of the moon occurred during the time of the Prophet Muhammad (PBUH) before the migration to Medina. Scholars of history, biography, hadith, and exegesis agree on this. According to their estimates, this event took place approximately five years before the migration, in the presence of the Prophet (PBUH) in Mecca. He was in Mina at the time. On this occasion, several companions and the disbelievers of the Quraysh witnessed it.
The commentator of Bukhari, Hafiz Ibn Hajar Asqalani, writes in Fath al-Bari under the narrations of the splitting of the moon:
قال: انشقّ القمر بمكة يعني: أن الانشقاق كان وهم بمكة قبل أن يهاجروا إلى المدينة
A narration states that the narrator (Abdullah ibn Masud) reported that the incident of the splitting of the moon occurred in Mecca. This means that when the moon was split into two parts, they were in Mecca before the migration to Medina. (7/184)
In Al-Mawahib Al-Ladunniyah, Allama Ahmad bin Muhammad Qastallani has written:
كان بمكة قبل الهجرة بنحو خمس سنين
This event took place in Mecca approximately five years before the Hijra. (2/254)
Maulana Abul A‘la Maududi has also specified this date. He writes:
The details that emerge from compiling all the narrations indicate that this incident occurred approximately five years before the migration. It was the fourteenth night of the lunar month. The moon had just risen. Suddenly, it split, and one fragment appeared on one side of the nearby mountain while the other fragment appeared on the other side. This phenomenon lasted only for a moment, and then the two fragments rejoined. The Prophet (PBUH) was present in Mina at that time. (Tafheem-ul-Qur’an 5/229)
Syed Sulaiman Nadvi states that this event was the final sign of guidance for the disbelievers of Quraysh. Even after witnessing such a great sign, when the Quraysh did not come to faith, Allah commanded the Prophet (PBUH) that the argument had been completed, and thus, he should leave this community and migrate. He writes:
Among the signs of guidance, the most conclusive and final sign for the disbelievers of Mecca was the splitting of the moon, after which the onset of destruction was imminent... Before the migration, the sign of the splitting of the moon appeared, and even upon witnessing it, when the leaders of the Quraysh did not embrace Islam, the Prophet Muhammad (PBUH) was commanded to migrate from Mecca, and the time for the punishment of destruction was near. Among the companions, those who were privy to the mysteries of prophethood had already understood that this migration was a precursor to the destruction of the Quraysh. In ‘Al-Mustadrak al-Hakim’ (Volume 3, p. 7) and ‘Musnad Ahmad ibn Hanbal’ (Volume 1, p. 216), it is mentioned that when the Prophet (PBUH) left Mecca, Abu Bakr Siddiq (RA) said, “Indeed, to Allah we belong. The people of Mecca have expelled their Messenger, surely they will be destroyed, and then the verse of battle (Udhina Lillazeena) was revealed.” (Seerat-un-Nabi 3/172-173)