At any rate...
“And by the Night when it departs;" 5. “Is there (not) in this an oath for those who have sense?" An Oath to the Dawn! There are five awakening oaths at the beginning of the Surah. At first, it says: "By the Break of Dawn," "And the Ten Nights;" The term /fajr/ originally means 'break open', and since the light of the dawn breaks the gloom of night it is called /fajr/.
We know that the meaning of /fajr/ is two fold: (1) /fajr-i-kaoib /'the false dawn' which rises without extending laterally and appears to be black, presenting itself like an obstacle on the horizon, and is compared to the tail of a Fox whose narrow end is onto the horizon and its conical shaped end is in, the mid-sky, (2) /fajr-i-sadiq/ ‘the true dawn' and is like a stream with white water that becomes visible, rising, filling the horizon with its whiteness and thereafter, spreads throughout the sky with a special brightness by which the night ends and the day begins.
It is the time when everything by which fasting would be broken becomes unlawful to the faster, and when the Morning Prayer can, then, be performed. Some commentators have carried the term /fajr/, in this verse, to its absolute meaning, that is; whiteness, which is certainly one of the signs of Allah's Greatness.
It is a reference point in the lives of human beings and all earthly creatures, and the prime glory of the victorious light and the end of faded darkness when the calm sleep ends and the movement of living creatures begins. It is for this very life that Allah swears by it. However, some commentators have said that it means 'break of dawn at the beginning of Muharram'.
Still, others have commented on it as meaning 'break of dawn on the day of the Feast of Sacrifice' where the important rituals of the pilgrimage to Mecca are fulfilled and it follows close to the Ten Nights. Finally, there are some who have commented on it as meaning 'break of dawn for the month of Ramadan', or 'break of dawn on Fridays'.