For what purpose did Allāh appoint a period of forty nights for Moses? When were these forty nights?

Imām Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

1. For receiving the Torah.
2. So that Allah speaks with him.

There are also two opinions concerning the period of this appointment:

1. It was the month of Dhū al-Qaʿdah and the first ten days of Dhū al-Ḥijjah. This is the view of those who say the appointment was in order to receive the Torah.
2. It was the month of Dhū al-Ḥijjah and the first ten days of Muḥarram. This is the view of those who say the appointment was for Allah to speak with Moses.